Calculate the missing check digit for GTIN-8, UPC-A, EAN-13 or GTIN-14 and see the complete identifier.
A check digit is the final digit of a barcode number, calculated from the preceding digits to help detect typing or scanning errors. A matching check digit confirms mathematical consistency, but does not prove that the number is registered or the product is genuine.
Use 7 digits for GTIN-8, 11 for UPC-A (GTIN-12), 12 for EAN-13 (GTIN-13) and 13 for GTIN-14. This calculator does not calculate UPC-E directly; expand UPC-E to UPC-A first.
From the rightmost body digit, multiply alternately by 3 and 1. Add the products. The check digit is the amount needed to reach the next multiple of ten, or zero if the sum is already a multiple of ten.
Worked example
Start with 12 digits:590123412345
Multiply each digit by its weight, alternating from the right.