v3.26.1
Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Mar. 31, 2026
Jun. 12, 2026
Sep. 30, 2025
Document Information [Line Items]      
Document Type 10-K    
Document Annual Report true    
Document Transition Report false    
Document Financial Statement Error Correction [Flag] false    
ICFR Auditor Attestation Flag false    
Entity Interactive Data Current Yes    
Amendment Flag false    
Document Period End Date Mar. 31, 2026    
Document Fiscal Year Focus 2026    
Document Fiscal Period Focus FY    
Entity Registrant Name INTERNATIONAL BATTERY METALS LTD.    
Entity Central Index Key 0001786318    
Entity File Number 333-286616    
Entity Tax Identification Number 00-0000000    
Entity Incorporation, State or Country Code Z4    
Current Fiscal Year End Date --03-31    
Entity Current Reporting Status Yes    
Entity Shell Company false    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Well-known Seasoned Issuer Yes    
Entity Ex Transition Period false    
Entity Voluntary Filers No    
Entity Public Float     $ 33.6
Entity Address, Address Line One 12 Greenway Plaza    
Entity Address, Address Line Two Suite 1100    
Entity Address, City or Town Houston    
Entity Address, State or Province TX    
Entity Address, Postal Zip Code 77046    
City Area Code 832    
Local Phone Number 683-8839    
Entity Common Stock, Shares Outstanding   377,601,682  
Auditor Firm ID 199    
Auditor Location Houston, Texas    
Auditor Name CBIZ CPAs P.C.    
Auditor Opinion [Text Block]

We have audited the accompanying consolidated balance sheets of International Battery Metals Ltd. (the “Company”) as of March 31, 2026 and 2025, the related consolidated statements of income (loss), cash flows, and changes in shareholders’ equity for the years ended March 31, 2026 and 2025, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of March 31, 2026 and 2025, and the results of its operations and its cash flows for the years ended March 31, 2026 and 2025, in conformity with accounting principles generally accepted in the United States of America.

    
Common Stock [Member]      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, no par value    
Trading Symbol IBAT    
Common Stock 1 [Member]      
Document Information [Line Items]      
Title of 12(b) Security Common Stock, no par    
Trading Symbol IBATF