GTIN Check Digit Calculator
Calculate or verify the check digit of a GTIN-8, UPC-A, EAN-13, GTIN-14, GLN, GSIN or SSCC with the GS1 mod-10 method, step by step.
Every GS1 identification number — the GTIN under a retail barcode, the GLN of a location, the SSCC on a pallet label — ends in a check digit that catches typing and scanning errors. Enter the number without its last digit to calculate it, or paste a complete code to verify it. The tool identifies the code type from the length and shows every step of the sum.
How to use this tool
- Enter the digits; spaces and dashes are ignored.
- Choose “Calculate check digit” for a number without its last digit, or “Verify full code” for a complete one.
- Read the check digit, the full code and the digit-by-digit table.
Formula
check digit = (10 − (Σ digit × weight) mod 10) mod 10, weights 3, 1, 3, 1 … starting from the rightmost digit
This is the GS1 General Specifications method used by every fixed-length GS1 key. Because the weights are counted from the right, leading zeros — a GTIN-12 written as a GTIN-14, for example — never change the check digit. Supported lengths: GTIN-8 (7 + 1), GTIN-12/UPC-A (11 + 1), GTIN-13/EAN-13/GLN (12 + 1), GTIN-14 (13 + 1), GSIN (16 + 1) and SSCC/GSRN (17 + 1).
Example
For 629104150021, the example on GS1’s own check-digit page, the digits from the right are multiplied by 3, 1, 3, 1 …: 1×3 + 2×1 + 0×3 + 0×1 + 5×3 + 1×1 + 4×3 + 0×1 + 1×3 + 9×1 + 2×3 + 6×1 = 57. The next multiple of ten is 60, so the check digit is 3 and the full GTIN-13 is 6291041500213.
Frequently asked questions
Does a correct check digit prove the barcode is genuine?
No. It only shows that the number is internally consistent. Whether a GTIN is really assigned to a product can be looked up in GS1’s Verified by GS1 service.
Which mistakes does the check digit catch?
Every single wrong digit, and almost every swap of two neighbouring digits — a swap goes unnoticed only when the two digits differ by 5, such as 0 and 5 or 2 and 7.
Does this work for ISBNs and ISSNs?
An ISBN-13 is a GTIN-13 beginning with 978 or 979, so yes. The older ISBN-10 uses a mod-11 check instead — use the ISBN converter for it.
My UPC has 12 digits but the tool says GTIN-14 — why?
In Calculate mode the tool adds a digit, so 13 entered digits make a GTIN-14. If your 12 or 13 digits already include the check digit, switch to Verify.
Sources
Last updated: 2026-10-30