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EAN-13 Barcode Check Digit Calculator

Check or generate the check digit of an EAN-13 barcode.

How it is calculated

The tool strips everything except digits, then works on the first 12. Starting from the left, digits in odd positions (1st, 3rd, 5th…) are multiplied by 1 and digits in even positions (2nd, 4th…) by 3. The weighted digits are added up, giving check = (10 − (sum mod 10)) mod 10. With 13 digits entered, the result compares this computed digit with your 13th digit and reports Valid or Invalid. With 12 digits entered, it reports the check digit and the complete 13-digit code. Any other length returns nothing. A valid check digit only means the code is internally consistent; it does not prove the product is registered.

Worked example

Check the code 4006381333931. Take the first 12 digits: 4 0 0 6 3 8 1 3 3 3 9 3. Odd positions (×1): 4 + 0 + 3 + 1 + 3 + 9 = 20. Even positions (×3): (0 + 6 + 8 + 3 + 3 + 3) × 3 = 23 × 3 = 69. Total: 89. 89 mod 10 = 9, and 10 − 9 = 1. The computed check digit is 1, which matches the last digit of the code, so the status is Valid.

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Common mistakes

  • Entering a 12-digit UPC-A code and expecting validation. With 12 digits the tool treats them as the base and computes a new check digit. To validate a UPC-A, put a 0 in front to make 13 digits.
  • Typos or transposed digits in the base. Swapping two adjacent digits usually changes the check digit, so a mismatch may point to a wrongly typed code, not a wrong barcode.
  • Entering 8-digit EAN-8 codes. Only 12 or 13 digits are accepted; other lengths return nothing.
  • Assuming a valid result means the product exists. Only the arithmetic is checked, not registration.
  • Leaving in spaces or hyphens and worrying about them. Non-digits are removed automatically, but a stray letter in place of a digit shifts every position.

About this calculator

This calculator validates or completes an EAN-13 barcode (the standard used on most retail products worldwide, and compatible with UPC-A). The check digit is computed by alternately weighting the first 12 digits by 1 and 3, summing them, and taking the amount needed to round up to the next multiple of 10.

Retailers, inventory and logistics staff, and developers building point-of-sale or warehouse systems use it to catch mistyped or corrupted barcodes before they cause scanning errors, and to generate a valid check digit when assigning a new product code. A full 13-digit code is verified, while the first 12 digits produce the missing check digit.

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Comments (1)

  • Editorial team

    The check digit catches typing slips, which makes it handy when you key codes in by hand. Because the weights are 1 and 3, any single wrong digit always changes the check digit, and so does swapping two neighbours unless they differ by exactly 5. A Valid status still says nothing about whether the code belongs to the product in your hand. Do you work with 12-digit UPC codes, and would a separate UPC-A mode help?

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