Free online code tools
Check digit calculator.
The last digit of a GTIN is a modulo-10 checksum. Work it out before you print, or verify a number a supplier sent you.
- No signup
- Free commercial use
- No watermarks
Paste 12 digits to calculate the check digit, or all 13 to verify one.
Result
Check digit 7
5901234123457
How the modulo-10 check digit works
Reading the number from the right, each digit is multiplied alternately by 3 and 1. The products are added together, and the check digit is whatever takes that sum up to the next multiple of ten. A valid check digit catches most single-digit typing mistakes and many transpositions, which is why scanners reject numbers that fail it.
Getting a valid check digit does not make a number yours. Retail identifiers are licensed by GS1 and ISBNs by your national agency.