Product barcode check digit

Client

Product barcode check digit is the rightmost digit on retail barcodes—computed with GS1 mod-10 alternating weights. Paste the full number to verify or see expected digit on failure.

Mod-10 on retail barcodes

Multiply digits by alternating 3 and 1 weights (from the right), sum, subtract from next higher ten—rightmost digit must match. Toolcore implements this on paste.

Privacy: every comparison runs locally in your tab. Toolcore performs no GS1 registry lookup, product database match, or price scan—checksum math only.
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GTIN‑8, UPC‑A (GTIN‑12), EAN‑13, and logistic GTIN‑14 all end with the same ISO/IEC GS1 modulus‑10 weight‑3 algorithm used by the barcode generator when it pads shortened bodies with a check digit. Alternate lengths map to retailer packaging standards (coupon GTIN‑12, carton GTIN‑14, compact GTIN‑8).

Result

Passes modulus‑10 GS1 rule for GTIN-13 (13 digits).

Common use cases

  • Fix one wrong digit on wholesale order forms.
  • Teach barcode structure with a working calculator link.
  • QA label proofs before print run.

Common mistakes to avoid

  • Confusing check digit with company prefix

    Check digit is always last; prefix digits identify GS1 company allocation.

  • Using Luhn formula from payment card docs

    Retail barcodes use GS1 mod-10—not Luhn doubling.

FAQ

Where is the check digit on a UPC?

The 12th (rightmost) digit on UPC-A barcodes.

Same algorithm for EAN-13?

Yes—GS1 mod-10 on the rightmost digit of 13-digit EAN.

Common search terms

Phrases people search for that match this tool. See the full long-tail keyword index.

  • gtin checksum verifier online
  • ean 13 check digit validate browser
  • upc-a modulus 10 checker locally
  • gtin 14 logistic barcode checksum
  • gs1 digit string validator no lookup

More tools

Related utilities you can open in another tab—mostly client-side.