The check digit is there to help ensure the number has been typed in correctly and can catch errors that may occur when the code is being created.
When you look at your list of GTINs in your GS1 UK Numberbank, it appears that your numbers aren’t sequential. This is because the last digit is generated from a special algorithm. If you ignore the check digit, you’ll see your numbers are listed in order.
Check digit calculator
Check digits for your GS1 identifiers may have already been calculated in My Numberbank. If not, they can can be manually calculated using the method described below or via our handy check digit calculator.
How to calculate a check digit
The following calculation can be used to create the check digit for all the GS1 Identification Keys that require them, including GTINs and GLNs.
Let’s take the GTIN 501234567000C as an example, where C is the check digit. This is how you calculate it:
| Step | What to do |
|---|---|
| 1 | Starting with the right-hand digit of the number, add all the alternate digit values |
| 2 | Multiply the result of step 1 by 3 |
| 3 | Add up all the other remaining digits |
| 4 | Add the result of step 2 to the result of step 3 |
| 5 | The check digit is the smallest number that must be added to this sum to reach a multiple of 10 |
So, to calculate the check digit of the number 501234567000C:
| Step | Calculation |
|---|---|
| 1 | 0 + 0 + 6 + 4 +2 + 0 = 12 |
| 2 | 12 x 3 = 36 |
| 3 | 0 + 7 + 5 + 3 + 1 + 5 = 21 |
| 4 | 36 + 21 = 57 |
| 5 | 57 + C = 60. Therefore, in this example, C = 3 |
| 6 | Therefore, the complete GTIN is 5012345670003 |