GS1 check digit calculator
Enter a number without its check digit and we calculate the last digit; or enter the full number and we tell you whether it is correct. You can paste a whole column from Excel: every line is checked separately.
One number per line. Spaces, hyphens and dots are ignored; prefixes such as (01), (00) or (414) are recognised.
The calculation runs only in your browser; the numbers you enter are not sent to any server.
Results appear here. Supported lengths (including the check digit): 8, 12, 13, 14, 17 and 18 digits.
01
How to use it
A
Choose the action: calculate the last digit, or verify an existing number.
B
Type a number or paste a column from Excel; every line is evaluated separately.
C
For a single number the calculation is shown step by step; for many lines, copy the results and paste them back into your sheet.
02
How is the check digit calculated?
The last digit of a GS1 number is a check digit calculated from the other digits. Working from right to left, the digits (excluding the check digit) are multiplied alternately by 3 and 1 and the products are added up; the check digit is the number that rounds the sum up to the next multiple of ten. If the sum already is a multiple of ten, the check digit is 0.
The method is the same for every GS1 number: trade item numbers (GTIN), location numbers (GLN), case and pallet numbers (SSCC), shipment numbers (GSIN) and service relation numbers (GSRN). It catches every single-digit typo and most swaps of two adjacent digits.
03
From 13 to 14 digits: a common mistake
Adding a leading 0 to a GTIN-13 does not change the check digit: the 14-digit form is the same number, and it is the form used in databases and in the (01) field of a GS1 barcode.
Deriving a new GTIN-14 for a case by adding an indicator digit (1–8) is different: the old check digit is dropped and a new one is calculated over the indicator digit and the remaining 12 digits. Simply putting the indicator digit in front of the 13-digit number produces an invalid number.
Another common mistake happens in Excel: when the column is formatted as a number, leading zeros are removed and a 14-digit GTIN shrinks to 13 digits. Format the column as text.
04
What does the prefix tell you?
The first digits are the start of the GS1 company prefix and show which GS1 member organisation allocated the number — 868 and 869 are GS1 Türkiye, for example. The prefix does not show the country of origin; a product made in one country can carry another country's prefix.
Numbers starting with 02, 04 or 2 are for restricted circulation (variable-weight items, internal codes); 977 is reserved for serial publications and 978–979 for books.
FAQ
- Are the numbers I enter sent anywhere?
- No. The calculation runs entirely in code inside your browser; the numbers are neither transmitted to a server nor stored.
- If the check digit is correct, is the number valid?
- No — it only shows that there is no typo. Whether the number has actually been allocated, and to which product, is checked with GS1's registry service (Verified by GS1) or your local GS1 organisation.
- Can I check several numbers at once?
- Yes. Copy a column from Excel and paste it; every line is evaluated separately and you can copy the results as tab-separated text back into your sheet. Up to 500 lines are processed at a time.
- Is a 13-digit number a GTIN or a GLN?
- Both have 13 digits and use the same check digit method, so the number alone does not tell them apart; the tool shows both. The same ambiguity applies to 18-digit SSCC and GSRN. If you enter the number with a prefix such as (01), (414) or (00), the type is taken from the prefix.
From master data to the line: are your numbers right?
In our serialization projects we tie GTIN and SSCC validation to master data entry and to the work order, so a wrong number is caught before it is printed on the line.