Check digit calculator

Type the digits without the last one and get the check digit, with every step of the sum shown. Paste a list to do hundreds at once.

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Check digit calculatortyping

EAN / UPC / GTINISBN-10

Digits without the check digit

7 digits → EAN-8 · 11 → UPC-A · 12 → EAN-13 · 13 → GTIN-14 · 17 → SSCC

Many numbers at once

One number per line, without check digits

[01] How it works3 steps

01
Pick the kind
EAN / UPC / GTIN for product, case and pallet numbers, or ISBN-10 for old book numbers.
02
Type the digits
Enter the number without its check digit: 11 digits for UPC-A, 12 for EAN-13, 7 for EAN-8, 13 for GTIN-14, 17 for SSCC.
03
Read the working
The check digit is shown with the full number, plus each digit, its weight and the total, so you can see where it comes from.

[02] Good to know2 notes

The GS1 formula (mod 10)

Used for EAN-13, EAN-8, UPC-A, GTIN-14, ITF-14, SSCC and GLN. Starting from the digit next to the check digit and moving left, multiply the digits by 3, 1, 3, 1 and so on. Add everything up. The check digit is what you add to reach the next multiple of 10.

Example: 400638133393, the first 12 digits of an EAN-13. From the right: 3×3 + 9×1 + 3×3 + 3×1 + 3×3 + 1×1 + 8×3 + 3×1 + 6×3 + 0×1 + 0×3 + 4×1 = 89. The next multiple of 10 is 90, so the check digit is 1 and the full barcode is 4006381333931. The calculator shows the weight under every digit, so you never have to count.

ISBN-10 (mod 11)

Old 10-digit ISBNs use a different rule: multiply the first nine digits by 10, 9, 8 … 2, add them up, and pick the check that makes the total divisible by 11. The check can come out as 10, which is written as X. ISBN-13s use the GS1 rule above.

Check a full barcode number Make a barcode with the right digit (sister site)

[03] Questions6

What is a check digit?

The last digit of a barcode number, calculated from all the others. Scanners recalculate it, and if it doesn't match they know a digit was misread.

How do you calculate a UPC check digit?

Take the 11 digits. Add the digits in odd positions (1st, 3rd…) and multiply by 3, then add the digits in even positions. The check digit is the amount needed to reach the next multiple of 10.

What is the check digit formula for EAN-13?

Weights 1 and 3 alternate from the left (1, 3, 1, 3…) over the first 12 digits. Add the products; the check digit takes the total up to the next multiple of 10. It is the same GS1 rule as UPC, counted from the right.

What is the difference between a check digit and a checksum?

A checksum is any value worked out from data to catch errors. A check digit is a checksum that is a single digit, added to the number itself.

Why does an ISBN end in X?

ISBN-10 uses a mod 11 check, so the check can be 10. It is written as the Roman numeral X to keep the ISBN at 10 characters.

Can I calculate many check digits at once?

Yes. Open Many numbers at once, paste one number per line (a column copied from a spreadsheet works), and download the results as a CSV file.