GS1 Check Digit
Arithmetic validation mechanism for GS1 keys.
Definition
The check digit is computed by weighting the key's digits alternately by 3 and 1, summing them, then taking the difference to the next multiple of ten, modulo 10. It applies to GTIN-8/12/13/14, the SSCC, the GLN and other fixed-length numeric keys.
Origin
The standard check-digit algorithm is defined in the GS1 General Specifications, section 7.9.
Example in context
For the partial GTIN-13 629104150021, the 3/1 weighting yields a check digit of 3, giving 6291041500213.