Every EAN-13, UPC-A, EAN-8 and ITF-14 barcode ends with a check digit — a final number calculated from the other digits that lets scanners catch typos and misprints. This free barcode check digit calculator computes it instantly, or validates a complete barcode you already have. No signup, no download — everything runs in your browser.
100% free · runs locally in your browser · your codes are never uploaded.
What Is a Barcode Check Digit?
The check digit is the last digit of a GTIN barcode (EAN-13, UPC-A, EAN-8, ITF-14). It is not random — it is calculated from the preceding digits using the GS1 modulo-10 algorithm. When a scanner reads a barcode, it recalculates the check digit; if it does not match, the scan is rejected. This single digit catches the vast majority of printing errors and data-entry typos before a bad barcode reaches your packaging.
How to Use the Calculator
To calculate: choose the “Calculate check digit” tab, enter your code without the last digit (12 digits for EAN-13, 11 for UPC-A, 7 for EAN-8, 13 for ITF-14), and hit Calculate. The tool shows your complete barcode number with the check digit highlighted, plus the step-by-step math.
To validate: switch to the “Validate a barcode” tab and enter the full number including the check digit. The tool tells you instantly whether it is valid — and if not, what the correct digit should be.
Which Barcodes Need Check Digits?
EAN-13 (13 digits) — the standard retail barcode outside North America. Enter 12 digits to calculate the 13th.
UPC-A (12 digits) — the North American retail standard. Enter 11 digits.
EAN-8 (8 digits) — for small products where EAN-13 will not fit. Enter 7 digits.
ITF-14 (14 digits) — for shipping cartons and outer packaging. Enter 13 digits.
Generating barcodes in bulk? Use our free bulk barcode generator to create up to 500 barcodes per batch, or the bulk EAN-13 generator and bulk UPC generator for retail codes.
Frequently Asked Questions
How is a barcode check digit calculated?
Using the GS1 modulo-10 method: starting from the rightmost digit (excluding the check digit), multiply alternate digits by 3 and 1, sum the results, and the check digit is (10 minus the sum mod 10) mod 10. The calculator above shows the full working.
What happens if my barcode has the wrong check digit?
Scanners will reject it, which means failed checkouts, rejected Amazon FBA shipments, and reprinted packaging. Always validate before you print.
Can I calculate a UPC check digit from 11 digits?
Yes — enter the 11 digits in the calculator and it returns the complete 12-digit UPC-A.
Is my data uploaded anywhere?
No. The calculation happens entirely in your browser. Nothing is sent or stored.