Quick answer
The EAN-13 check digit is calculated from the first 12 digits. Starting from the left, add digits in odd positions and three times the digits in even positions. The check digit is the amount needed to bring the total up to the next multiple of ten.
How to do it
- Write the first 12 digits without spaces or punctuation.
- Add the odd-position digits and three times the even-position digits.
- Subtract the final total's last digit from ten, using zero when it is already a multiple of ten.
A short example
For 400638133393, the weighted calculation produces a total whose next multiple of ten requires 1, so the complete valid value is 4006381333931. A validator repeats that calculation and compares the result with the thirteenth digit.
What validation does not prove
A correct check digit detects many typing and scanning errors, but it does not prove that the number was licensed, identifies the claimed product, or is registered in a retail database. Obtain real GTINs through the appropriate GS1 organization.
Common mistakes to avoid
- Counting positions from the wrong end or starting at zero.
- Dropping leading zeros in a spreadsheet.
- Treating a valid checksum as proof of ownership.
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