EAN-13 Check Digit Calculator

What is EAN-13 Check Digit Calculator?

The last digit of an EAN-13 is a check digit. It is calculated from the other twelve so that scanners can detect a mistyped or misread number. A code whose 13th digit does not match the first 12 is invalid, and most tills will reject it.

The rule is simple. Add up the digits in odd positions (1st, 3rd, 5th and so on), add up the digits in even positions, multiply the even sum by 3 and add the two results. The check digit is the number that brings the total up to the next multiple of 10, which is written (10 − sum mod 10) mod 10.

The same calculation, with the same weights read from the right, is used for EAN-8, UPC-A, GTIN-14 and SSCC codes, which is why one method covers most retail and logistics numbers.

When should you use it?

• You are building an EAN-13 by hand and need its last digit.
• A supplier spreadsheet contains 13-digit numbers that you want to sanity-check.
• A scan fails and you want to know whether the printed number is even valid.
• You are learning or teaching how retail barcodes work.
• You want to complete a code that is missing its final digit.

The formula with a worked example

Take the first 12 digits 590123412345. Number the positions 1 to 12 from the left: the digits are 5, 9, 0, 1, 2, 3, 4, 1, 2, 3, 4, 5.

Step 1, odd positions (1, 3, 5, 7, 9, 11): 5 + 0 + 2 + 4 + 2 + 4 = 17.

Step 2, even positions (2, 4, 6, 8, 10, 12): 9 + 1 + 3 + 1 + 3 + 5 = 22.

Step 3, total: 17 + 3 × 22 = 17 + 66 = 83.

Step 4, check digit: (10 − 83 mod 10) mod 10 = (10 − 3) mod 10 = 7. The full code is 5901234123457.

To validate a full 13-digit code, apply steps 1 to 4 to the first 12 digits and compare the result with the 13th digit. Alternatively, weight all 13 digits (1 for odd positions, 3 for even positions, the 13th digit having weight 1) and add them up: the total must be a multiple of 10. For 5901234123457 the sum is 83 + 7 = 90, so it is valid.

This check catches every single-digit error and most swaps of two adjacent digits. The exception is a swap of two neighbouring digits that differ by exactly 5, which the formula cannot detect.

Privacy

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The calculation is plain JavaScript on your device. Numbers you type are not sent or stored anywhere.