How is the check digit calculated?

Using the GS1 modulo-10 method: from the rightmost data digit, multiply digits alternately by 3 and 1, add the products, then the check digit is (10 − sum mod 10) mod 10. EAN-13, UPC-A and EAN-8 all share this algorithm.

What is the difference between the formats?

EAN-13 is a 13-digit code (12 data + 1 check) used worldwide; UPC-A is the 12-digit North American code (11 data + 1 check); EAN-8 is a compact 8-digit code (7 data + 1 check) for small packages.

Does this validate ISBN barcodes?

Yes for the barcode itself — a 13-digit ISBN printed as a barcode is an EAN-13 and uses this exact check digit. Note the older 10-digit ISBN uses a different modulo-11 scheme, so use an ISBN-specific tool for those.

Barcode Check Digit Calculator (UPC, EAN)

Retail barcodes — EAN-13, UPC-A and EAN-8 — end with a single check digit computed from all the digits before it using the GS1 modulo-10 algorithm. Starting from the rightmost data digit, digits are weighted alternately by 3 and 1, the weighted values are summed, and the check digit is whatever brings that sum up to the next multiple of ten. This tool works both ways: type the data digits (12 for EAN-13, 11 for UPC-A, 7 for EAN-8) and it returns the check digit and the complete code, or paste a full barcode and it confirms whether the printed check digit is correct. Non-digit characters such as spaces and hyphens are ignored. Everything runs locally in your browser — nothing is uploaded.

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FormatBarcode digits

Enter the data digits to compute the check digit, or the full code to verify it. Spaces and hyphens are ignored.

Check digit7

Complete code

5901234123457

How to use

Pick the barcode format: EAN-13, UPC-A or EAN-8.
Enter the data digits without the check digit to calculate it, or the full code to verify it.
Read the check digit and copy the complete code (its check digit is highlighted).
Try EAN-13 data 400638133393 — the check digit is 1, giving 4006381333931.

Frequently asked questions

How is the check digit calculated?: Using the GS1 modulo-10 method: from the rightmost data digit, multiply digits alternately by 3 and 1, add the products, then the check digit is (10 − sum mod 10) mod 10. EAN-13, UPC-A and EAN-8 all share this algorithm.
What is the difference between the formats?: EAN-13 is a 13-digit code (12 data + 1 check) used worldwide; UPC-A is the 12-digit North American code (11 data + 1 check); EAN-8 is a compact 8-digit code (7 data + 1 check) for small packages.
Does this validate ISBN barcodes?: Yes for the barcode itself — a 13-digit ISBN printed as a barcode is an EAN-13 and uses this exact check digit. Note the older 10-digit ISBN uses a different modulo-11 scheme, so use an ISBN-specific tool for those.

Guides on this topic

How Barcode Check Digits Work (EAN-13, UPC-A, EAN-8) A clear, practical explanation of the GS1 modulo-10 check digit on retail barcodes — how it is calculated, why it catches errors, and how to validate a code by hand.

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