GS1 Check Digit Calculator
Enter a number without its last digit to calculate it, or enter the whole number to check that it is right.
Enter 12 digits to calculate the check digit, or all 13 to test one.
Everything runs in your browser. What you type is never sent to us.
The result appears here as you type.
What a check digit does
The last digit of every GS1 number is calculated from the digits before it. When a scanner or a person enters the number, the system repeats the calculation. If the result does not match, the number is treated as wrong. This catches most typing errors and misreads.
How it is calculated
- Starting from the right, leave out the check digit position and multiply the digits alternately by 3 and 1.
- Add up the results.
- Subtract the total from the next multiple of 10. The answer is the check digit.
Take 590123412345. Working from the right, the weighted digits add up to 83. The next multiple of 10 is 90, so the check digit is 7, and the full number is 5901234123457.
Which number types this covers
The same method works for GTIN-8, GTIN-12 (UPC-A), GTIN-13 (EAN-13), GTIN-14 (ITF-14), GLN location numbers and SSCC pallet codes. Once you have the full number, draw it with the barcode generator.
A correct check digit only proves the number is well formed. It does not show that the number is registered to you or to anyone else.
What this tool does and does not do
It draws the barcode for the number you enter. It does not issue numbers: retail barcodes need a number licensed from GS1.
Scan a printed sample before a full run. Print quality, material and color all affect scanning, and only a barcode verifier gives a formal grade.
Common questions
Does a valid check digit mean the barcode number is mine to use?
No. Anyone can calculate a valid check digit. For retail, the number must come from your GS1 company prefix.
Why do my 12 digits give a different answer for GTIN-12 and GTIN-13?
Twelve digits are a complete GTIN-12, so the tool tests the last one. For GTIN-13, those same 12 digits come before the check digit, so the tool calculates a new one.
Does the calculator store my numbers?
No. The calculation runs in your browser, so the numbers are not sent to Asas Label.
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