How the GS1 check digit works
- Start from the rightmost digit (the one next to where the check digit will go).
- Multiply it by 3, the next one by 1, the next by 3, and so on, alternating.
- Add all the results together.
- Find the difference to the next multiple of 10. That difference (0–9) is the check digit.
When to use it
Checking a number before printing
Catch a typo before thousands of packs are printed.
Building GTIN-14 case codes
Work out the new check digit after adding an indicator digit.
Spreadsheets and systems
Verify the formula in your own system gives the same result.
Worked example: EAN-13 590123412345?
Digits from the right: 5,4,3,2,1,4,3,2,1,0,9,5. Weighted 3,1,3,1…: 15+4+9+2+3+4+9+2+3+0+27+5 = 83. The next multiple of 10 is 90, so the check digit is 7, giving 5901234123457.
Notes
- This uses the GS1 modulo-10 method, which covers EAN, UPC, ITF-14, GTIN, GLN and SSCC.
- ISBN-10 uses a different modulo-11 method; enter ISBN-10 on the ISBN barcode page to convert it.
Questions people ask
What does the check digit protect against?
It catches all single-digit mistakes and most swaps of two neighbouring digits.
Why is my check digit 0?
When the weighted sum is already a multiple of 10, the check digit is 0.
Last updated 11 October 2026 by the QRizeo team.