GTIN, UPC, EAN and ISBN check digit validator
Paste one barcode per line (straight from a spreadsheet column is fine). Each one is checked against the GS1 check digit rule, and the results flag the usual spreadsheet damage and the prefixes Google Merchant Center rejects.
Runs entirely in your browser. Nothing you paste leaves this page.
What the results mean
- Invalid, check digit should be N. The last digit doesn't match the other digits. Usually one of the other digits was mistyped, so don't just change the last digit: compare the number with the barcode printed on the product or the supplier's sheet.
- 11 digits, probably lost its leading zero. Excel and Google Sheets treat barcodes as numbers and drop leading zeros. A UPC-A always has 12 digits. How to stop spreadsheets from doing this.
- Scientific notation (3.6E+11). The spreadsheet has already rounded the number, so the original digits are gone. Type it in again from the source.
- Restricted or coupon prefix. Numbers starting 2, 02 or 04 are for in-store or variable-weight use, and 05, 98 and 99 are coupon ranges. The check digit can be right, but Google Merchant Center still won't accept them as product GTINs.
- Contains letters. That's a custom code (like a SKU), not a GTIN. It's fine to keep in Shopify's barcode field as a custom barcode, but don't send it to Google as a GTIN.
- Appears N times. The same GTIN appears more than once. A UPC and its 13-digit form with a leading zero count as one code. Every variant you sell should have its own GTIN. Find duplicates in a full product export.
How the check digit works
Every GTIN (GTIN-8, UPC-A/GTIN-12, EAN-13/GTIN-13, GTIN-14) ends in a check digit. Starting from the digit just before it and moving left, multiply each digit by 3, then 1, then 3, and so on. Add the results. The check digit is whatever brings that total up to the next multiple of 10. ISBN-10 uses a different rule (weights 10 down to 2, modulo 11, where X stands for 10), and the tool also converts a valid ISBN-10 to its ISBN-13 form.
A correct check digit only means the number is well formed. It doesn't prove the GTIN was assigned to your product. Only the brand owner's GS1 record can show that.
GS1 explains the calculation on its check digit page. Google's GTIN rules are in the Merchant Center GTIN help.