How to calculate a GS1 check digit
Apply alternating weights of 3 and 1, total the products, and follow a complete GTIN-13 example from weighted sum to check digit.
Read guideUnderstand the final digit
GS1 Mod-10, identifier lengths, and honest validation
Three focused guides explain the alternating-weight algorithm, the roles of GTIN, GLN, and SSCC, and the strict boundary between a valid check digit and a verified identity.
GTIN, GLN, and SSCC identifiers explained
Compare the purpose and complete length of six supported GS1 identifier formats that share one check digit algorithm.
Read guideWhat a check digit can—and cannot—verify
Separate arithmetic integrity from GS1 assignment, product identity, ownership, authenticity, and barcode print quality.
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