<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019eb749-3065-7b6c-9c33-609bde265b84,g:d9e64205-6b52-48f2-a018-3146b6936118-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="https://xbrl.org/2023/arcrole/summation-item" xlink:type="simple" xlink:href="https://www.xbrl.org/2023/calculation-1.1.xsd#summation-item"/>
  <link:roleRef roleURI="http://www.firstib.com/role/CondensedConsolidatedBalanceSheets" xlink:type="simple" xlink:href="inbk-20260630.xsd#CondensedConsolidatedBalanceSheets"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019eb749-3603-7fe1-9a7d-ba50254bc22f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb749-3603-71e7-b103-05e64f023b4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019eb749-3603-7fe1-9a7d-ba50254bc22f" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb749-3603-71e7-b103-05e64f023b4c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019eb749-3603-75c0-86f0-7ec61c0bb3a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019eb749-3603-7fe1-9a7d-ba50254bc22f" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest_019eb749-3603-75c0-86f0-7ec61c0bb3a0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb749-3603-706e-8bc0-11a17bcf30e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestBearingDepositsInBanks_019eb749-3603-7165-b370-20e5e33f8014" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestBearingDepositsInBanks"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb749-3603-706e-8bc0-11a17bcf30e8" xlink:to="loc_us-gaap_InterestBearingDepositsInBanks_019eb749-3603-7165-b370-20e5e33f8014" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndDueFromBanks_019eb749-3603-76a2-a31d-600fa9d3a06e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndDueFromBanks"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb749-3603-706e-8bc0-11a17bcf30e8" xlink:to="loc_us-gaap_CashAndDueFromBanks_019eb749-3603-76a2-a31d-600fa9d3a06e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BankOwnedLifeInsurance_019eb749-3603-73d6-8181-41267be4c961" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BankOwnedLifeInsurance"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_BankOwnedLifeInsurance_019eb749-3603-73d6-8181-41267be4c961" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_019eb749-3603-7721-b2d3-20a502d023a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServicingAsset"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_ServicingAsset_019eb749-3603-7721-b2d3-20a502d023a0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRealEstate_019eb749-3603-7e7a-9fea-8aec54ac8eeb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherRealEstate"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_OtherRealEstate_019eb749-3603-7e7a-9fea-8aec54ac8eeb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestReceivable_019eb749-3603-7363-88c5-ea22abba93b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestReceivable"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_InterestReceivable_019eb749-3603-7363-88c5-ea22abba93b7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalHomeLoanBankStock_019eb749-3603-79c9-a8d2-7fd6254d36c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalHomeLoanBankStock"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_FederalHomeLoanBankStock_019eb749-3603-79c9-a8d2-7fd6254d36c6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019eb749-3603-7bac-829a-0fd3b7c58bb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssets"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_OtherAssets_019eb749-3603-7bac-829a-0fd3b7c58bb7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019eb749-3603-75b4-a26e-ff4c28b77574" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019eb749-3603-75b4-a26e-ff4c28b77574" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019eb749-3603-7afa-b361-411428499778" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_Goodwill_019eb749-3603-7afa-b361-411428499778" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb749-3603-7928-b5fd-97aa3558af1f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:calculationArc order="9" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019eb749-3603-7928-b5fd-97aa3558af1f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019eb749-3603-71f8-9583-63f4cddeaddd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss"/>
    <link:calculationArc order="10" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAfterAllowanceForCreditLoss_019eb749-3603-71f8-9583-63f4cddeaddd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019eb749-3603-7e80-a6cb-dbf82c1ba774" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:calculationArc order="11" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_019eb749-3603-7e80-a6cb-dbf82c1ba774" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss_019eb749-3603-7e8c-ad48-0fa0f7836bf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss"/>
    <link:calculationArc order="12" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss_019eb749-3603-7e8c-ad48-0fa0f7836bf9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019eb749-3603-795c-9221-3cf1f157beb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Assets_019eb749-3603-7f8d-a110-e2ebd73ce9d4" xlink:to="loc_us-gaap_LoansReceivableHeldForSaleNetNotPartOfDisposalGroup_019eb749-3603-795c-9221-3cf1f157beb7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019eb749-3603-796c-8330-e9cedfab5c90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019eb749-3603-72b5-939d-8d89dc5edb03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019eb749-3603-796c-8330-e9cedfab5c90" xlink:to="loc_us-gaap_Liabilities_019eb749-3603-72b5-939d-8d89dc5edb03" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019eb749-3603-72b7-8fb6-8bb7a70a32b7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019eb749-3603-796c-8330-e9cedfab5c90" xlink:to="loc_us-gaap_StockholdersEquity_019eb749-3603-72b7-8fb6-8bb7a70a32b7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019eb749-3603-7511-9e08-3914df32283e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquity_019eb749-3603-796c-8330-e9cedfab5c90" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019eb749-3603-7511-9e08-3914df32283e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019eb749-3603-7b06-b77a-98491358357c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_019eb749-3603-75bc-9570-62cfd5ce4301" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019eb749-3603-7b06-b77a-98491358357c" xlink:to="loc_us-gaap_PreferredStockValue_019eb749-3603-75bc-9570-62cfd5ce4301" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019eb749-3603-7113-b953-88a1ce1b5acf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019eb749-3603-7b06-b77a-98491358357c" xlink:to="loc_us-gaap_CommonStockValue_019eb749-3603-7113-b953-88a1ce1b5acf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019eb749-3603-7f95-9886-0d8ac7df2154" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019eb749-3603-7b06-b77a-98491358357c" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019eb749-3603-7f95-9886-0d8ac7df2154" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019eb749-3603-7e98-b72a-bcc5ccf5d3f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_StockholdersEquity_019eb749-3603-7b06-b77a-98491358357c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019eb749-3603-7e98-b72a-bcc5ccf5d3f3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Deposits_019eb749-3603-75d9-8c14-156700b76cbf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Deposits"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestBearingDepositLiabilities_019eb749-3603-7d72-bdfe-c6c28951eda3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestBearingDepositLiabilities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Deposits_019eb749-3603-75d9-8c14-156700b76cbf" xlink:to="loc_us-gaap_NoninterestBearingDepositLiabilities_019eb749-3603-7d72-bdfe-c6c28951eda3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestBearingDepositLiabilities_019eb749-3603-7048-8893-5f9a8d9c810f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestBearingDepositLiabilities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Deposits_019eb749-3603-75d9-8c14-156700b76cbf" xlink:to="loc_us-gaap_InterestBearingDepositLiabilities_019eb749-3603-7048-8893-5f9a8d9c810f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019eb749-3603-7364-bf72-ab6e7b0e4f00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Deposits_019eb749-3603-72df-9b2d-74895aae7a56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Deposits"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019eb749-3603-7364-bf72-ab6e7b0e4f00" xlink:to="loc_us-gaap_Deposits_019eb749-3603-72df-9b2d-74895aae7a56" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdvancesFromFederalHomeLoanBanks_019eb749-3603-7990-868c-e8c4304f23ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdvancesFromFederalHomeLoanBanks"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019eb749-3603-7364-bf72-ab6e7b0e4f00" xlink:to="loc_us-gaap_AdvancesFromFederalHomeLoanBanks_019eb749-3603-7990-868c-e8c4304f23ac" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebt_019eb749-3603-7f9a-96b6-a83928d978e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubordinatedDebt"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019eb749-3603-7364-bf72-ab6e7b0e4f00" xlink:to="loc_us-gaap_SubordinatedDebt_019eb749-3603-7f9a-96b6-a83928d978e3" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019eb749-3603-7300-9b3d-34c7ecbe087f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019eb749-3603-7364-bf72-ab6e7b0e4f00" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019eb749-3603-7300-9b3d-34c7ecbe087f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_019eb749-3603-7b19-8df7-9b32829d9514" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccruedLiabilitiesAndOtherLiabilities"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_Liabilities_019eb749-3603-7364-bf72-ab6e7b0e4f00" xlink:to="loc_us-gaap_AccruedLiabilitiesAndOtherLiabilities_019eb749-3603-7b19-8df7-9b32829d9514" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/CondensedConsolidatedStatementsofOperationsUnaudited" xlink:type="simple" xlink:href="inbk-20260630.xsd#CondensedConsolidatedStatementsofOperationsUnaudited"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/CondensedConsolidatedStatementsofOperationsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestExpense"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019eb749-3603-7133-ae31-0072816a72cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019eb749-3603-7133-ae31-0072816a72cb" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketingAndAdvertisingExpense_019eb749-3603-765e-b329-c18045167ef9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketingAndAdvertisingExpense"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_MarketingAndAdvertisingExpense_019eb749-3603-765e-b329-c18045167ef9" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019eb749-3603-767b-ae87-79336eaba212" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfessionalFees"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_ProfessionalFees_019eb749-3603-767b-ae87-79336eaba212" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InformationTechnologyAndDataProcessing_019eb749-3603-7444-a73b-4e17361fa52f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InformationTechnologyAndDataProcessing"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_InformationTechnologyAndDataProcessing_019eb749-3603-7444-a73b-4e17361fa52f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanProcessingFee_019eb749-3603-7156-9b2f-7bba0eee09b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoanProcessingFee"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_LoanProcessingFee_019eb749-3603-7156-9b2f-7bba0eee09b5" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OccupancyNet_019eb749-3603-781c-a326-a87019b5f93f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OccupancyNet"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_OccupancyNet_019eb749-3603-781c-a326-a87019b5f93f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalDepositInsuranceCorporationPremiumExpense_019eb749-3603-7e60-88a6-1fbfc47f95f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FederalDepositInsuranceCorporationPremiumExpense"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_FederalDepositInsuranceCorporationPremiumExpense_019eb749-3603-7e60-88a6-1fbfc47f95f8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoninterestExpense_019eb749-3603-70c2-be63-b0a71b2fb38e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNoninterestExpense"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestExpense_019eb749-3603-7db6-99d3-cb96b05ca75f" xlink:to="loc_us-gaap_OtherNoninterestExpense_019eb749-3603-70c2-be63-b0a71b2fb38e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOperating_019eb749-3603-7f91-9ff0-47409c46a55e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseOperating"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDeposits_019eb749-3603-7bf9-91ae-7f584f228c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDeposits"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseOperating_019eb749-3603-7f91-9ff0-47409c46a55e" xlink:to="loc_us-gaap_InterestExpenseDeposits_019eb749-3603-7bf9-91ae-7f584f228c6a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseBorrowings_019eb749-3603-7248-a2b8-b5a99a81beec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseBorrowings"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestExpenseOperating_019eb749-3603-7f91-9ff0-47409c46a55e" xlink:to="loc_us-gaap_InterestExpenseBorrowings_019eb749-3603-7248-a2b8-b5a99a81beec" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7104-ba6e-298845e957ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestAndDividendIncomeOperating"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndFeeIncomeLoansAndLeases_019eb749-36a5-78fa-a9c0-82a75a3c9517" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestAndFeeIncomeLoansAndLeases"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7104-ba6e-298845e957ad" xlink:to="loc_us-gaap_InterestAndFeeIncomeLoansAndLeases_019eb749-36a5-78fa-a9c0-82a75a3c9517" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeSecuritiesTaxable_019eb749-36a5-7b19-9905-5de136d4ee2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeSecuritiesTaxable"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7104-ba6e-298845e957ad" xlink:to="loc_us-gaap_InterestIncomeSecuritiesTaxable_019eb749-36a5-7b19-9905-5de136d4ee2b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeSecuritiesTaxExempt_019eb749-36a5-779e-8d27-ae95d6a61adc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeSecuritiesTaxExempt"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7104-ba6e-298845e957ad" xlink:to="loc_us-gaap_InterestIncomeSecuritiesTaxExempt_019eb749-36a5-779e-8d27-ae95d6a61adc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOther_019eb749-36a5-746e-ab28-242c40bba5c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeOther"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7104-ba6e-298845e957ad" xlink:to="loc_us-gaap_InterestIncomeOther_019eb749-36a5-746e-ab28-242c40bba5c4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncome_019eb749-3603-7d7e-9ddd-1d4657d65e9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncome"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019eb749-3603-7791-a3e7-2b70d10bc8d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestIncome_019eb749-3603-7d7e-9ddd-1d4657d65e9a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019eb749-3603-7791-a3e7-2b70d10bc8d8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncomeOtherOperatingIncome_019eb749-3603-789f-aef5-f40c7734e71e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncomeOtherOperatingIncome"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestIncome_019eb749-3603-7d7e-9ddd-1d4657d65e9a" xlink:to="loc_us-gaap_NoninterestIncomeOtherOperatingIncome_019eb749-3603-789f-aef5-f40c7734e71e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfOtherLoansAndLeases_019eb749-3603-74d7-b80f-6b3f43f6c030" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfOtherLoansAndLeases"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NoninterestIncome_019eb749-3603-7d7e-9ddd-1d4657d65e9a" xlink:to="loc_us-gaap_GainLossOnSaleOfOtherLoansAndLeases_019eb749-3603-74d7-b80f-6b3f43f6c030" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019eb749-3603-72ad-a145-4b0be0ce17a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-791e-9eb3-612421580d1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019eb749-3603-72ad-a145-4b0be0ce17a9" xlink:to="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-791e-9eb3-612421580d1e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestExpense_019eb749-3603-70e9-b2e2-7ef176615108" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestExpense"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019eb749-3603-72ad-a145-4b0be0ce17a9" xlink:to="loc_us-gaap_NoninterestExpense_019eb749-3603-70e9-b2e2-7ef176615108" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoninterestIncome_019eb749-3603-78ca-95ec-e1d3ad91bcd2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoninterestIncome"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019eb749-3603-72ad-a145-4b0be0ce17a9" xlink:to="loc_us-gaap_NoninterestIncome_019eb749-3603-78ca-95ec-e1d3ad91bcd2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019eb749-3603-7361-a890-1be219798b66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019eb749-3603-7b11-9c6e-dd650acbdf72" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019eb749-3603-7361-a890-1be219798b66" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019eb749-3603-7b11-9c6e-dd650acbdf72" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019eb749-3603-7e5f-a74a-c3307ab28e9e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetIncomeLoss_019eb749-3603-7361-a890-1be219798b66" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019eb749-3603-7e5f-a74a-c3307ab28e9e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_019eb749-36a5-73ac-95fd-af665ec58db0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseOperating_019eb749-36a5-7468-8e6e-e1b06892646a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseOperating"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestIncomeExpenseNet_019eb749-36a5-73ac-95fd-af665ec58db0" xlink:to="loc_us-gaap_InterestExpenseOperating_019eb749-36a5-7468-8e6e-e1b06892646a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7c12-9937-5eef4408b2c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestAndDividendIncomeOperating"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestIncomeExpenseNet_019eb749-36a5-73ac-95fd-af665ec58db0" xlink:to="loc_us-gaap_InterestAndDividendIncomeOperating_019eb749-36a5-7c12-9937-5eef4408b2c4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-7402-b36f-ad2d3165a049" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityCreditLossExpenseReversal_019eb749-3603-7f31-b82b-7e5f29ce3200" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityCreditLossExpenseReversal"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-7402-b36f-ad2d3165a049" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityCreditLossExpenseReversal_019eb749-3603-7f31-b82b-7e5f29ce3200" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal_019eb749-3603-7792-928c-1b6480d6e14d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-7402-b36f-ad2d3165a049" xlink:to="loc_us-gaap_OffBalanceSheetCreditLossLiabilityCreditLossExpenseReversal_019eb749-3603-7792-928c-1b6480d6e14d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_019eb749-3603-7093-9757-5472389ebe33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-7402-b36f-ad2d3165a049" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_019eb749-3603-7093-9757-5472389ebe33" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForLoanLossesExpensed_019eb749-36a5-744d-8c03-93909f9ab28b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProvisionForLoanLossesExpensed"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss_019eb749-3603-7402-b36f-ad2d3165a049" xlink:to="loc_us-gaap_ProvisionForLoanLossesExpensed_019eb749-36a5-744d-8c03-93909f9ab28b" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeUnaudited" xlink:type="simple" xlink:href="inbk-20260630.xsd#CondensedConsolidatedStatementsofComprehensiveIncomeUnaudited"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/CondensedConsolidatedStatementsofComprehensiveIncomeUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019eb749-36a5-78ea-81e5-c9a2670d5a07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax_019eb749-36a5-764d-b480-48b9ed889c18" xlink:href="inbk-20260630.xsd#inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019eb749-36a5-78ea-81e5-c9a2670d5a07" xlink:to="loc_inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax_019eb749-36a5-764d-b480-48b9ed889c18" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities_019eb749-36a5-7467-be31-0ca22b4501fe" xlink:href="inbk-20260630.xsd#inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019eb749-36a5-78ea-81e5-c9a2670d5a07" xlink:to="loc_inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities_019eb749-36a5-7467-be31-0ca22b4501fe" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax_019eb749-36a5-7423-a285-e5f0a807f946" xlink:href="inbk-20260630.xsd#inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_OtherComprehensiveIncomeLossTaxOnHeldToMaturitySecurities_019eb749-36a5-7d4e-b417-ca737fcb755c" xlink:href="inbk-20260630.xsd#inbk_OtherComprehensiveIncomeLossTaxOnHeldToMaturitySecurities"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax_019eb749-36a5-7423-a285-e5f0a807f946" xlink:to="loc_inbk_OtherComprehensiveIncomeLossTaxOnHeldToMaturitySecurities_019eb749-36a5-7d4e-b417-ca737fcb755c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax_019eb749-36a5-7221-8a4a-1e050f3ec520" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_inbk_OCIDebtSecuritiesHeldToMaturityGainLossAfterAdjustmentAndTax_019eb749-36a5-7423-a285-e5f0a807f946" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax_019eb749-36a5-7221-8a4a-1e050f3ec520" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019eb749-36a5-7adb-9c45-f8d652632787" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019eb749-36a5-7af1-9fc5-4144ed914087" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019eb749-36a5-7adb-9c45-f8d652632787" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_019eb749-36a5-7af1-9fc5-4144ed914087" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019eb749-36a5-768c-ade9-cf25dd978c44" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTax_019eb749-36a5-7adb-9c45-f8d652632787" xlink:to="loc_us-gaap_NetIncomeLoss_019eb749-36a5-768c-ade9-cf25dd978c44" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities_019eb749-36a5-7e8f-8e2a-38d05ffd0283" xlink:href="inbk-20260630.xsd#inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsAndTax_019eb749-36a5-7a9f-98d7-59c67b0954d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsAndTax"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities_019eb749-36a5-7e8f-8e2a-38d05ffd0283" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeReclassificationAdjustmentsAndTax_019eb749-36a5-7a9f-98d7-59c67b0954d1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_OtherComprehensiveIncomeLossTaxOnAvailableForSaleSecurities_019eb749-36a5-7957-b81f-4eaf01d40662" xlink:href="inbk-20260630.xsd#inbk_OtherComprehensiveIncomeLossTaxOnAvailableForSaleSecurities"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_inbk_OtherComprehensiveIncomeLossNetOfTaxOnAvailableForSaleSecurities_019eb749-36a5-7e8f-8e2a-38d05ffd0283" xlink:to="loc_inbk_OtherComprehensiveIncomeLossTaxOnAvailableForSaleSecurities_019eb749-36a5-7957-b81f-4eaf01d40662" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/CondensedConsolidatedStatementsofCashFlowsUnaudited" xlink:type="simple" xlink:href="inbk-20260630.xsd#CondensedConsolidatedStatementsofCashFlowsUnaudited"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/CondensedConsolidatedStatementsofCashFlowsUnaudited" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_PaymentsForProceedsLoansAndLeasesExcludingPurchases_019eb749-36a5-73a8-84eb-86fe5334590c" xlink:href="inbk-20260630.xsd#inbk_PaymentsForProceedsLoansAndLeasesExcludingPurchases"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_inbk_PaymentsForProceedsLoansAndLeasesExcludingPurchases_019eb749-36a5-73a8-84eb-86fe5334590c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_ProceedsFromLiquidationOfRealEstateOwned_019eb749-36a5-755c-a84d-1edb65cd190f" xlink:href="inbk-20260630.xsd#inbk_ProceedsFromLiquidationOfRealEstateOwned"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_inbk_ProceedsFromLiquidationOfRealEstateOwned_019eb749-36a5-755c-a84d-1edb65cd190f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_019eb749-36a5-76c7-a902-8b06ac1e9f6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities_019eb749-36a5-76c7-a902-8b06ac1e9f6f" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_019eb749-36a5-7fd6-84c5-549c713e557b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt_019eb749-36a5-7fd6-84c5-549c713e557b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfHeldToMaturitySecurities_019eb749-36a5-76ac-b744-8ce51eab5d90" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleAndMaturityOfHeldToMaturitySecurities"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfHeldToMaturitySecurities_019eb749-36a5-76ac-b744-8ce51eab5d90" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireHeldToMaturitySecurities_019eb749-36a5-7fa4-a88c-9eb1a79de81d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireHeldToMaturitySecurities"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_PaymentsToAcquireHeldToMaturitySecurities_019eb749-36a5-7fa4-a88c-9eb1a79de81d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019eb749-36a5-720f-acdb-acfde6193159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:calculationArc order="7" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_019eb749-36a5-720f-acdb-acfde6193159" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireLoansReceivable_019eb749-36a5-77c0-bd11-6e3d3d013868" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireLoansReceivable"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_PaymentsToAcquireLoansReceivable_019eb749-36a5-77c0-bd11-6e3d3d013868" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019eb749-36a5-71cb-9f0c-d21a9e6659cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-7cd6-904a-7df6da945cb3" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019eb749-36a5-71cb-9f0c-d21a9e6659cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019eb749-36a5-7c77-8105-2fa61c36542e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_NetIncomeLoss_019eb749-36a5-7c77-8105-2fa61c36542e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019eb749-36a5-72d4-ac44-0c7110438496" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019eb749-36a5-72d4-ac44-0c7110438496" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_IncreaseDecreaseInCashSurrenderValueOfLifeInsurance_019eb749-36a5-7586-9ddd-856c65757993" xlink:href="inbk-20260630.xsd#inbk_IncreaseDecreaseInCashSurrenderValueOfLifeInsurance"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_inbk_IncreaseDecreaseInCashSurrenderValueOfLifeInsurance_019eb749-36a5-7586-9ddd-856c65757993" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForLoanLeaseAndOtherLosses_019eb749-36a5-7a93-82ff-400de7e3d142" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProvisionForLoanLeaseAndOtherLosses"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_ProvisionForLoanLeaseAndOtherLosses_019eb749-36a5-7a93-82ff-400de7e3d142" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019eb749-36a5-7877-bb87-1b342169643d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensation"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_ShareBasedCompensation_019eb749-36a5-7877-bb87-1b342169643d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForOriginationAndPurchasesOfLoansHeldForSale_019eb749-36a5-73d6-b5ff-6497e6f08286" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForOriginationAndPurchasesOfLoansHeldForSale"/>
    <link:calculationArc order="6" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_PaymentsForOriginationAndPurchasesOfLoansHeldForSale_019eb749-36a5-73d6-b5ff-6497e6f08286" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfLoansHeldForSale_019eb749-36a5-728b-bf35-889eacc75794" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfLoansHeldForSale"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_ProceedsFromSaleOfLoansHeldForSale_019eb749-36a5-728b-bf35-889eacc75794" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSalesOfLoansNet_019eb749-36a5-765c-a4eb-1d8ebd2998f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSalesOfLoansNet"/>
    <link:calculationArc order="8" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_GainLossOnSalesOfLoansNet_019eb749-36a5-765c-a4eb-1d8ebd2998f4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnSalesOfOtherRealEstate_019eb749-36a5-7f23-87ac-565a8e0b1302" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainsLossesOnSalesOfOtherRealEstate"/>
    <link:calculationArc order="9" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_GainsLossesOnSalesOfOtherRealEstate_019eb749-36a5-7f23-87ac-565a8e0b1302" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_GainLossOnDerivatives_019eb749-36a5-7c07-925a-20be7396373a" xlink:href="inbk-20260630.xsd#inbk_GainLossOnDerivatives"/>
    <link:calculationArc order="10" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_inbk_GainLossOnDerivatives_019eb749-36a5-7c07-925a-20be7396373a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_inbk_IncreaseDecreaseInServicingAssets_019eb749-36a5-779c-89f9-31dfdd452d47" xlink:href="inbk-20260630.xsd#inbk_IncreaseDecreaseInServicingAssets"/>
    <link:calculationArc order="11" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_inbk_IncreaseDecreaseInServicingAssets_019eb749-36a5-779c-89f9-31dfdd452d47" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019eb749-36a5-78e4-aa92-e0f775a92c63" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:calculationArc order="12" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_019eb749-36a5-78e4-aa92-e0f775a92c63" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_019eb749-36a5-78e4-8b77-a26e2d27460b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities"/>
    <link:calculationArc order="13" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7689-b7dc-35d07b49c142" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilitiesAndOtherOperatingLiabilities_019eb749-36a5-78e4-8b77-a26e2d27460b" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019eb749-36a5-7ffc-a5e0-3441d2a94782" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7980-8807-b05736a3b76e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019eb749-36a5-7ffc-a5e0-3441d2a94782" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019eb749-36a5-7980-8807-b05736a3b76e" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-794c-8e06-0e2ae29020fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019eb749-36a5-7ffc-a5e0-3441d2a94782" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019eb749-36a5-794c-8e06-0e2ae29020fc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7d6c-b500-01ff611eb1cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019eb749-36a5-7ffc-a5e0-3441d2a94782" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7d6c-b500-01ff611eb1cf" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7b77-8261-0c9c0d155394" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeposits_019eb749-36a5-7874-b25f-3084622460aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInDeposits"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7b77-8261-0c9c0d155394" xlink:to="loc_us-gaap_IncreaseDecreaseInDeposits_019eb749-36a5-7874-b25f-3084622460aa" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividends_019eb749-36a5-7c11-81a3-ff30fd508e2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsOfDividends"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7b77-8261-0c9c0d155394" xlink:to="loc_us-gaap_PaymentsOfDividends_019eb749-36a5-7c11-81a3-ff30fd508e2a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromFederalHomeLoanBankBorrowings_019eb749-36a5-7454-a20f-b62bc4f6b6c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromFederalHomeLoanBankBorrowings"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7b77-8261-0c9c0d155394" xlink:to="loc_us-gaap_ProceedsFromFederalHomeLoanBankBorrowings_019eb749-36a5-7454-a20f-b62bc4f6b6c8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfFederalHomeLoanBankBorrowings_019eb749-36a5-7952-ac11-c6aad4d2ef92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RepaymentsOfFederalHomeLoanBankBorrowings"/>
    <link:calculationArc order="4" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7b77-8261-0c9c0d155394" xlink:to="loc_us-gaap_RepaymentsOfFederalHomeLoanBankBorrowings_019eb749-36a5-7952-ac11-c6aad4d2ef92" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019eb749-36a5-73e5-8c20-be5269074b42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019eb749-36a5-7b77-8261-0c9c0d155394" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019eb749-36a5-73e5-8c20-be5269074b42" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/LossEarningsPerShareDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#LossEarningsPerShareDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/LossEarningsPerShareDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019eb749-36a5-7c24-b278-95986aaee250" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019eb749-36a5-7bae-b9a1-9f03d362839d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019eb749-36a5-7c24-b278-95986aaee250" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019eb749-36a5-7bae-b9a1-9f03d362839d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019eb749-36a5-7525-9f93-37df34d3b420" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019eb749-36a5-7c24-b278-95986aaee250" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019eb749-36a5-7525-9f93-37df34d3b420" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/SecuritiesDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#SecuritiesDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/SecuritiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss_019eb749-36a5-74a9-9829-03c3159d638b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecurities_019eb749-36a5-7591-b3a4-9cb744c99ca7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecurities"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss_019eb749-36a5-74a9-9829-03c3159d638b" xlink:to="loc_us-gaap_HeldToMaturitySecurities_019eb749-36a5-7591-b3a4-9cb744c99ca7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss_019eb749-36a5-7b32-8d83-c8708b9075f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtSecuritiesHeldToMaturityAmortizedCostAfterAllowanceForCreditLoss_019eb749-36a5-74a9-9829-03c3159d638b" xlink:to="loc_us-gaap_DebtSecuritiesHeldToMaturityAllowanceForCreditLoss_019eb749-36a5-7b32-8d83-c8708b9075f7" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/SecuritiesCarryingValueDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#SecuritiesCarryingValueDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/SecuritiesCarryingValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-78d8-a6a5-1148625d53ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost_019eb749-36a5-7097-ab4b-a534df25e470" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-78d8-a6a5-1148625d53ce" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCost_019eb749-36a5-7097-ab4b-a534df25e470" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost_019eb749-36a5-750d-9a65-51bfa439d547" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-78d8-a6a5-1148625d53ce" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingAfterTenYearsAmortizedCost_019eb749-36a5-750d-9a65-51bfa439d547" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost_019eb749-36a5-78b9-a834-d456bc475131" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-78d8-a6a5-1148625d53ce" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCost_019eb749-36a5-78b9-a834-d456bc475131" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost_019eb749-36a5-7d00-8fc4-1226173d1847" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-78d8-a6a5-1148625d53ce" xlink:to="loc_us-gaap_HeldtomaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCost_019eb749-36a5-7d00-8fc4-1226173d1847" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019eb749-36a5-7ec4-b6d2-ca9ea3ed2302" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_019eb749-36a5-7e75-84c1-9292039d97ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019eb749-36a5-7ec4-b6d2-ca9ea3ed2302" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_019eb749-36a5-7e75-84c1-9292039d97ce" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_019eb749-36a5-70c2-9d15-62f4ed2fe34d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019eb749-36a5-7ec4-b6d2-ca9ea3ed2302" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_019eb749-36a5-70c2-9d15-62f4ed2fe34d" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_019eb749-36a5-7199-a50d-4bfc8b27246c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019eb749-36a5-7ec4-b6d2-ca9ea3ed2302" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_019eb749-36a5-7199-a50d-4bfc8b27246c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue_019eb749-36a5-767e-8aac-7022eedcffd2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_019eb749-36a5-7ec4-b6d2-ca9ea3ed2302" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenFairValue_019eb749-36a5-767e-8aac-7022eedcffd2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue_019eb749-36a5-71ef-a1c1-211826048fb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_019eb749-36a5-7d69-bdcf-65b82af36388" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue_019eb749-36a5-71ef-a1c1-211826048fb2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearSixThroughTenFairValue_019eb749-36a5-7d69-bdcf-65b82af36388" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_019eb749-36a5-7439-9da8-f092f0cd0ee4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue_019eb749-36a5-71ef-a1c1-211826048fb2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValue_019eb749-36a5-7439-9da8-f092f0cd0ee4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_019eb749-36a5-708f-97ea-ba5e7c618683" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue_019eb749-36a5-71ef-a1c1-211826048fb2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue_019eb749-36a5-708f-97ea-ba5e7c618683" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue_019eb749-36a5-75f4-bff9-d553d059ec1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesSingleMaturityDateFairValue_019eb749-36a5-71ef-a1c1-211826048fb2" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue_019eb749-36a5-75f4-bff9-d553d059ec1a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-7e5b-b33d-06c4ff336a30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis_019eb749-36a5-7b49-9f56-ec31d2b1defd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-7e5b-b33d-06c4ff336a30" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis_019eb749-36a5-7b49-9f56-ec31d2b1defd" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis_019eb749-36a5-73e6-a418-66c9f43fe56a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-7e5b-b33d-06c4ff336a30" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterYearTenAmortizedCostBasis_019eb749-36a5-73e6-a418-66c9f43fe56a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis_019eb749-36a5-776f-941b-5356f3d66eda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-7e5b-b33d-06c4ff336a30" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveAmortizedCostBasis_019eb749-36a5-776f-941b-5356f3d66eda" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis_019eb749-36a5-7f4c-a2c0-97461dedc0df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_019eb749-36a5-7e5b-b33d-06c4ff336a30" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenAmortizedCostBasis_019eb749-36a5-7f4c-a2c0-97461dedc0df" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/SecuritiesGrossUnrealizedLossesandFairValueDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#SecuritiesGrossUnrealizedLossesandFairValueDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/SecuritiesGrossUnrealizedLossesandFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019eb749-36a5-71ea-9169-9ecd48fd3af5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019eb749-36a5-78f2-b95c-3e861eec9cb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019eb749-36a5-71ea-9169-9ecd48fd3af5" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months_019eb749-36a5-78f2-b95c-3e861eec9cb6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019eb749-36a5-7240-b674-bd009eea0af4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition_019eb749-36a5-71ea-9169-9ecd48fd3af5" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_019eb749-36a5-7240-b674-bd009eea0af4" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019eb749-36a5-7d16-87f2-aaba8dddfd15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019eb749-36a5-71d0-a0b3-29ebd830d004" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019eb749-36a5-7d16-87f2-aaba8dddfd15" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_019eb749-36a5-71d0-a0b3-29ebd830d004" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019eb749-36a5-7b22-86b6-25a2a2887a11" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss_019eb749-36a5-7d16-87f2-aaba8dddfd15" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss_019eb749-36a5-7b22-86b6-25a2a2887a11" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/LoansCreditRiskProfileandLoanPortfolioDelinquencyDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#LoansCreditRiskProfileandLoanPortfolioDelinquencyDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/LoansCreditRiskProfileandLoanPortfolioDelinquencyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019eb749-36a5-7101-a87c-46c6d6450d27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff_019eb749-36a5-7101-a87c-46c6d6450d27" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019eb749-36a5-7f98-a426-e39961687785" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff_019eb749-36a5-7f98-a426-e39961687785" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-734e-8903-afcc9450166c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-734e-8903-afcc9450166c" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-764d-8b85-4e2ba909c737" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-764d-8b85-4e2ba909c737" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-7520-9641-327134ce062a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-7520-9641-327134ce062a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019eb749-36a5-7bd9-9d29-091ae3c6d547" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff_019eb749-36a5-7bd9-9d29-091ae3c6d547" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-708f-88d4-a68cfe094ea2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff_019eb749-36a5-708f-88d4-a68cfe094ea2" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019eb749-36a5-7ff5-9619-6fec892c1184" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff_019eb749-36a5-7b00-966e-cdda6cdb8807" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff_019eb749-36a5-7ff5-9619-6fec892c1184" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019eb749-36a5-77ff-97b7-6895de5c2e51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear_019eb749-36a5-77ff-97b7-6895de5c2e51" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019eb749-36a5-727c-b673-91395318e337" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear_019eb749-36a5-727c-b673-91395318e337" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019eb749-36a5-7726-bc38-8b80aa7b31f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear"/>
    <link:calculationArc order="3" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear_019eb749-36a5-7726-bc38-8b80aa7b31f7" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019eb749-36a5-7df5-89bf-72c5c8f40857" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear"/>
    <link:calculationArc order="4" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear_019eb749-36a5-7df5-89bf-72c5c8f40857" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019eb749-36a5-72f7-b3b5-4c478f38f75a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear"/>
    <link:calculationArc order="5" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear_019eb749-36a5-72f7-b3b5-4c478f38f75a" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019eb749-36a5-76aa-b9f1-abd8f59679e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan"/>
    <link:calculationArc order="6" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan_019eb749-36a5-76aa-b9f1-abd8f59679e6" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019eb749-36a5-70ef-870b-a62eda9e5c95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestRevolving"/>
    <link:calculationArc order="7" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestRevolving_019eb749-36a5-70ef-870b-a62eda9e5c95" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019eb749-36a5-7846-9382-b5c1c52436b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear"/>
    <link:calculationArc order="8" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7e3d-8148-288570761eff" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear_019eb749-36a5-7846-9382-b5c1c52436b0" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb749-36a5-7dfd-a771-3d46099545c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7b06-ba74-28f3e26f2723" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb749-36a5-7dfd-a771-3d46099545c4" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossFeeAndLoanInProcess_019eb749-36a5-7b06-ba74-28f3e26f2723" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_019eb749-36a5-7889-ac61-b481ca5c3285" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss_019eb749-36a5-7dfd-a771-3d46099545c4" xlink:to="loc_us-gaap_FinancingReceivableUnamortizedLoanCommitmentOriginationFeeAndPremiumDiscount_019eb749-36a5-7889-ac61-b481ca5c3285" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/PremisesandEquipmentSummaryDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#PremisesandEquipmentSummaryDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/PremisesandEquipmentSummaryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019eb749-36a5-7f79-b8e0-f40a75c06dc6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019eb749-36a5-75d9-90ff-6ca2b9ef8bf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:calculationArc order="1" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_019eb749-36a5-7f79-b8e0-f40a75c06dc6" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019eb749-36a5-75d9-90ff-6ca2b9ef8bf1" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019eb749-36a5-78ba-909e-37b66d0fb605" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:calculationArc order="2" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentNet_019eb749-36a5-7f79-b8e0-f40a75c06dc6" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019eb749-36a5-78ba-909e-37b66d0fb605" xlink:type="arc"/>
  </link:calculationLink>
  <link:roleRef roleURI="http://www.firstib.com/role/AccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="inbk-20260630.xsd#AccumulatedOtherComprehensiveLossDetails"/>
  <link:calculationLink xlink:role="http://www.firstib.com/role/AccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb749-375a-703d-9ead-00f08ab68c43" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_019eb749-375a-7daf-969c-8060bddd15dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb749-375a-703d-9ead-00f08ab68c43" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_019eb749-375a-7daf-969c-8060bddd15dc" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019eb749-375a-7b8d-9639-f9cbc6f7a388" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019eb749-375a-703d-9ead-00f08ab68c43" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019eb749-375a-7b8d-9639-f9cbc6f7a388" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019eb749-375a-7e16-b2e5-309ab3d986f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019eb749-375a-794b-a5ce-f58eea907de8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent"/>
    <link:calculationArc order="1" weight="-1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019eb749-375a-7e16-b2e5-309ab3d986f5" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent_019eb749-375a-794b-a5ce-f58eea907de8" xlink:type="arc"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019eb749-375a-7024-b9df-2ed9b413e9f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent"/>
    <link:calculationArc order="2" weight="1.0" xlink:arcrole="https://xbrl.org/2023/arcrole/summation-item" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_019eb749-375a-7e16-b2e5-309ab3d986f5" xlink:to="loc_us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent_019eb749-375a-7024-b9df-2ed9b413e9f0" xlink:type="arc"/>
  </link:calculationLink>
</link:linkbase>
