SSCC-18 check digit calculator
Enter the first 17 digits of an SSCC to get its check digit, or all 18 to verify one. The calculation runs in your browser and every step is shown. The same method checks a GTIN or a GLN.
17 digits. For an SSCC: extension digit, GS1 Company Prefix and serial reference, 17 in all.
Check digit: 2
006141410000000012
The working
- Starting from the right, multiply each digit by 3, then 1, then 3, and so on.
- Add the results: 48.
- Subtract from the next multiple of ten: 50 - 48 = 2.
| Digit | 0 | 0 | 6 | 1 | 4 | 1 | 4 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Weight | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 |
| Product | 0 | 0 | 18 | 1 | 12 | 1 | 12 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 |
How the SSCC check digit is calculated
The last digit of an SSCC is not part of the serial number. It is calculated from the 17 digits before it, so that a mistyped or misread digit shows up as a number that does not add up. The method is the standard GS1 check digit, set out in section 7.9.1 of the GS1 General Specifications:
- Starting with the digit next to the check digit and working left, multiply the digits alternately by 3 and by 1.
- Add up the results.
- Subtract the sum from the nearest equal or higher multiple of ten. The answer is the check digit.
GS1's own worked example
Table 7-9 of the General Specifications works through an 18-digit number. The first 17 digits are 37610425002123456:
| Digit | 3 | 7 | 6 | 1 | 0 | 4 | 2 | 5 | 0 | 0 | 2 | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Multiply by | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 | 1 | 3 |
| Result | 9 | 7 | 18 | 1 | 0 | 4 | 6 | 5 | 0 | 0 | 6 | 1 | 6 | 3 | 12 | 5 | 18 |
The results add up to 101. The next multiple of ten is 110, and 110 minus 101 is 9. The complete number is 376104250021234569. These are the same figures GS1 prints in the table, and this site's tests check the calculator against them.
The same digit on a GTIN or GLN
GS1 states that the algorithm is identical for all its fixed length numeric data structures that carry a check digit (section 7.9.1). The weights always start with 3 on the digit beside the check digit, so the calculator above handles a GTIN-8, GTIN-12, GTIN-13, GTIN-14 or a 13-digit GLN as well. Enter the number without its last digit to calculate, or switch to verify and enter all of it.
What a correct check digit does not tell you
It confirms the 18 digits are consistent with each other. It does not confirm that the company prefix is yours, or that you have not used the number before. Uniqueness is the part that depends on your own records. See the SSCC label guide for how the number is structured and carton label for numbering a run.
There is also a second, unrelated check inside the barcode itself: the Code 128 symbol check character, explained on the GS1-128 label page.
The label generator calculates the check digit for every label it numbers, and verifies any SSCC you paste in.
Open the label generatorSources
- GS1 General Specifications Standard. GS1. Release 26.0, ratified January 2026. Read 9 October 2026.