EAN-13 Check Digit Calculator – Free Online Tool

Position	Digit	Multiplier	Value
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What Is a Barcode Check Digit Calculator?

A check digit calculator helps you find or verify the final digit of a barcode number.

Every GS1 barcode — including EAN-13, UPC-A, EAN-8, and ITF-14 — ends with a check digit. This digit is mathematically derived from the preceding digits using the Mod-10 algorithm, and its purpose is to catch scanning or data entry errors.

This tool works in two modes: calculate the missing check digit from a base number, or validate whether the check digit on an existing barcode is correct.

Calculate vs Validate Mode

The tool automatically switches mode based on how many digits you enter:

Calculate mode — enter the base digits (e.g. 12 digits for EAN-13). The tool calculates and appends the correct check digit.
Validate mode — enter the full barcode (e.g. 13 digits for EAN-13). The tool checks whether the check digit is correct.

Supported Barcode Formats

This tool supports all GS1 barcode formats that use the Mod-10 check digit algorithm:

EAN-13 — enter 12 digits to calculate, 13 digits to validate
UPC-A — enter 11 digits to calculate, 12 digits to validate
EAN-8 — enter 7 digits to calculate, 8 digits to validate
ITF-14 — enter 13 digits to calculate, 14 digits to validate

Note: Code128 and Code39 do not use a user-facing check digit and are not applicable here. Use the Barcode Analyzer for those formats.

How the Mod-10 Algorithm Works

The check digit is calculated using the GS1 Mod-10 (modulo 10) algorithm:

Starting from the left, multiply odd-position digits by 1 and even-position digits by 3
Sum all the resulting values
Divide the sum by 10 and take the remainder
If the remainder is 0, the check digit is 0. Otherwise, subtract the remainder from 10

This tool shows the full step-by-step breakdown so you can verify the calculation yourself.

Frequently Asked Questions

What is a barcode check digit?

A check digit is the last digit of a barcode number. It is calculated from the preceding digits using the Mod-10 algorithm and is used to verify that the barcode was scanned or entered correctly.

How is the EAN-13 check digit calculated?

The EAN-13 check digit uses the GS1 Mod-10 algorithm. Odd-position digits are multiplied by 1, even-position digits by 3. The products are summed, and the check digit is 10 minus the remainder when divided by 10 (or 0 if the remainder is already 0).

What is the difference between calculate and validate mode?

Calculate mode takes 12 digits (EAN-13 base) and computes the missing 13th check digit. Validate mode takes a full 13-digit barcode and checks whether the check digit is correct.

Does this tool support UPC-A and EAN-8?

Yes. The tool automatically detects the format based on how many digits you enter. It supports EAN-8 (7–8 digits), UPC-A (11–12 digits), EAN-13 (12–13 digits), and ITF-14 (13–14 digits).

Why is my barcode check digit wrong?

Common causes are a typo in one of the digits, a digit transposition, or the barcode number being from a different format than expected. Use this tool to calculate what the correct check digit should be.

Barcode Check Digit Calculator