GTIN-8 / EAN-8 Check Digit Calculator

How it is calculated

Only digits are read; spaces and dashes are stripped. The code must then have exactly 7 or 8 digits, otherwise there is no result. The first 7 digits are weighted alternately 3, 1, 3, 1, 3, 1, 3 from the left and added: sum = 3·d1 + d2 + 3·d3 + d4 + 3·d5 + d6 + 3·d7. The check digit is (10 − sum mod 10) mod 10, the amount that brings the sum up to the next multiple of 10. With 7 digits the tool returns the check digit and the full 8-digit code. With 8 digits it compares your last digit with the computed one and reports Valid or Invalid. A valid check digit only proves the number is well formed, not that the product is registered.

Common mistakes

• Applying the EAN-13 weighting (1 first, then 3). For EAN-8 the first digit is multiplied by 3.
• Including the check digit in the sum when computing it. Only the first 7 digits are used.
• Entering 12 or 13 digits of an EAN-13 or UPC-A code. Only 7 or 8 digits are accepted.
• Assuming a valid check digit means the barcode is registered. It only shows that no digit was mistyped in a typical way.
• Typing an 8-digit code with a missing or extra digit and reading the result as a failed check, when the count itself is wrong.