Barcode Check Digit Calculator (UPC, EAN)

Using the GS1 modulo-10 method: from the rightmost data digit, multiply digits alternately by 3 and 1, add the products, then the check digit is (10 − sum mod 10) mod 10. EAN-13, UPC-A and EAN-8 all share this algorithm.

EAN-13 is a 13-digit code (12 data + 1 check) used worldwide; UPC-A is the 12-digit North American code (11 data + 1 check); EAN-8 is a compact 8-digit code (7 data + 1 check) for small packages.

Yes for the barcode itself — a 13-digit ISBN printed as a barcode is an EAN-13 and uses this exact check digit. Note the older 10-digit ISBN uses a different modulo-11 scheme, so use an ISBN-specific tool for those.

Because the check digit only proves the number was read correctly, not that it identifies what you think. A GS1 number is assigned to a company prefix and then to an item by that company, so a valid code can belong to a product you have never heard of, to a reused number from a discontinued line, or to a range someone bought for internal use. Validity is a property of the digits; identity comes from the catalogue.

Because the same item is often registered separately by each distributor, and because the packaging differs: a different size, a multipack or a regional variant is a different item and gets its own number. The leading digits indicate which national organisation issued the company prefix rather than where the product was made, which is a common misreading of them.