v3.26.1
Document And Entity Information - shares
 3 Months Ended
Mar. 31, 2026
May 14, 2026
Document And Entity Information    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-39281  
Entity Registrant Name TMC the metals Co Inc.  
Entity Incorporation, State or Country Code A1  
Entity Tax Identification Number 00-0000000  
Entity Address, Address Line One 1111 West Hastings Street  
Entity Address, Address Line Two 15th Floor  
Entity Address, City or Town Vancouver  
Entity Address, State or Province BC  
Entity Address, Postal Zip Code V6E 2J3  
City Area Code 888  
Local Phone Number 458-3420  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   433,221,138
Entity Central Index Key 0001798562  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Common Shares, without par value    
Document And Entity Information    
Title of 12(b) Security Common Shares, without par value  
Trading Symbol TMC  
Security Exchange Name NASDAQ  
Redeemable warrants, each whole warrant exercisable for one Common Share, each at an exercise price of $11.50 per share    
Document And Entity Information    
Title of 12(b) Security Redeemable warrants, each whole warrant exercisable for one Common Share, each at an exercise price of $11.50 per share  
Trading Symbol TMCWW  
Security Exchange Name NASDAQ