Validate an EAN code and calculate the check digit

Checking an EAN code: how to use the checker

This EAN checker tells you whether a barcode number is valid and calculates the correct check digit. Paste one code or a whole column of codes into the input field and choose Validate. The checker recognises the type by the number of digits: 8 digits is an EAN-8, 12 a UPC-A, 13 an EAN-13 and 14 a GTIN-14. Spaces, dashes and dots are ignored, so 978-0-306-40615-7 or 8711 0000 0000 7 are recognised just fine. If you copy several columns from Excel, the tool uses the first non-empty cell on each line.

For a single code you see straight away whether it is valid, what the correct check digit is and which GS1 prefix it contains. For a valid EAN-13 or EAN-8 we also show a preview of the barcode. For a list you get a table with the status per line, counters for valid, invalid and duplicate, a filter to show only the errors, and the option to copy the result or download it as a CSV.

If your code is missing its last digit, for example because you assign numbers yourself within your GS1 range, choose Calculate check digit. The tool completes 7, 11, 12 or 13 digits into a full EAN-8, UPC-A, EAN-13 or GTIN-14. That choice is deliberately explicit: twelve digits can be either a complete UPC-A or an EAN-13 without its check digit, and no tool can guess which one you mean.

How the check digit of an EAN or GTIN works

All GS1 codes use the same modulo 10 calculation. Take the digits without the last one and start from the right: multiply the rightmost digit by 3, the next by 1, then by 3 again, and so on. Add everything up and see how much you need to reach the next multiple of ten. That number (0 to 9) is the check digit. For 871100000000 the sum is 33, so the check digit is 7 and the complete EAN-13 is 8711000000007.

Because the weighting starts from the right, a leading zero does not change the check digit. A UPC-A with a zero in front is therefore also a valid EAN-13, and an EAN-13 with a zero in front a valid GTIN-14. The check digit catches every single-digit error and most swaps of two adjacent digits. It says nothing about whether the code has actually been assigned to your product: for that you need the registration with GS1.

What the GS1 prefix does and does not tell you

The first two or three digits of an EAN-13 form the GS1 prefix. 870 to 879 is issued by GS1 Netherlands, 540 to 549 by GS1 Belgium and Luxembourg, and 400 to 440 by GS1 Germany. The prefix indicates the country of the GS1 membership, not the country of origin. A Dutch company that manufactures in Asia simply uses an 87 code, and a foreign brand with a Dutch subsidiary can do the same.

Some ranges are not meant for global product codes. Codes starting with 20 to 29 are for internal use, such as weighed items where the weight or price is part of the code. They are only unique within one shop or company. 977 is reserved for periodicals (ISSN) and 978 and 979 for books (ISBN). Codes starting with 0 or 1 usually come from the United States or Canada, where UPC-A is the standard.

Common mistakes in product files

The most common mistake happens in Excel. To Excel, an EAN-13 is a number, and long numbers are displayed as 8.71E+12. Once you save that file, the last digits are gone for good. Leading zeros also disappear without warning, so a 12-digit UPC-A suddenly has 11 digits. Set the column to Text before pasting or importing. The checker recognises both cases and tells you so.

Other classics are duplicate codes in a product file, for example because a variant was given the code of the base product by mistake, and codes made up without GS1 registration. The latter can have a correct check digit and still be rejected by marketplaces and retailers, who check whether the code belongs to your company prefix. Use the checker as a first filter, and if in doubt, look up in the GS1 registry who a code belongs to.

If you work with thousands of items, several suppliers or a webshop connected to marketplaces, you do not want to do these checks by hand. Have them run automatically when supplier files are imported and before products are published, so a wrong code never reaches your ERP, WMS or webshop.