Check Digits and Check Digit Calculators

Recently, I’ve received a lot of questions regarding the check digit, or last digit in a UPC barcode. In order to calculate the check digit, which is based on the previous eleven numbers in the UPC, the following needs to be performed:

  • Add all of the digits in odd-numbered positions together and multiply the sum by three
  • Add all of the digits in even-numbered positions
  • Add the two sums together

The check digit will be the number it would take to round to the nearest multiple of 10. If the sums of your digits was 66, then, 66 + x = 70, where x represents the check digit and 70 represents the nearest multiple of 10. In this case, the check digit would be 4.

If all of this still seems confusing, then no need to worry. The GS1 has put together a GTIN and SSCC check digit calculator, also including an informative chart on how to calculate it manually.