GTIN Check Digit Calculator & Validator
Calculate missing check digits or validate complete barcode numbers for GTIN-14, GTIN-13 (EAN-13), GTIN-12 (UPC-A), and GTIN-8 using official GS1 Modulo-10 algorithms with step-by-step mathematical proof.
Enter 7 digits (GTIN-8), 11 digits (UPC-A), 12 digits (EAN-13), or 13 digits (GTIN-14) to calculate the final check digit.
Quick Presets
How Does the GS1 Check Digit Calculation Work?
The check digit is a redundancy check used for error detection in all standard GS1 identification keys (GTIN-8, GTIN-12, GTIN-13, GTIN-14, and SSCC-18). It detects single-digit typing mistakes and transposition errors (such as swapping two adjacent digits).
All GS1 standards use the Modulo-10 algorithm with alternating weights of 3 and 1 calculated from right to left:
Step-by-Step Calculation Procedure:
- Count from Right to Left: Starting with the position immediately preceding the check digit, assign alternating weight multipliers of 3, then 1, then 3, then 1 all the way to the first digit.
- Multiply Digits by Weights: Multiply each individual barcode digit by its assigned weight factor.
- Sum the Products: Add all the multiplied results together to obtain a total sum.
- Modulo 10 Calculation: Divide the sum by 10 and determine the remainder. Subtract the remainder from 10. If the remainder is 0, the check digit is 0.
| Barcode Type | Data Digits | Check Digit Position | Weight Pattern (Left to Right) |
|---|---|---|---|
| GTIN-8 (EAN-8) | 7 digits | 8th digit | 3, 1, 3, 1, 3, 1, 3 |
| GTIN-12 (UPC-A) | 11 digits | 12th digit | 3, 1, 3, 1, 3, 1, 3, 1, 3, 1, 3 |
| GTIN-13 (EAN-13) | 12 digits | 13th digit | 1, 3, 1, 3, 1, 3, 1, 3, 1, 3, 1, 3 |
| GTIN-14 (ITF-14) | 13 digits | 14th digit | 3, 1, 3, 1, 3, 1, 3, 1, 3, 1, 3, 1, 3 |
Common Check Digit Validation Errors & How to Fix Them
1. Swapped Digits (Transposition)
Accidentally typing "54" instead of "45" changes the weighted sum dramatically, triggering an immediate check digit mismatch error.
2. Incorrect Digit Count
Missing leading zeros on 12-digit UPCs or pasting a 14-digit GTIN without checking container packaging causes length validation failures.
3. Amazon Error 5461 / 8572
Even if your check digit is mathematically valid, Amazon may reject your listing if the GS1 company prefix does not match your brand owner records in GS1 GEPIR.
Frequently Asked Questions
Can this tool calculate check digits for Amazon FBA or Walmart barcodes?
Yes. Amazon and Walmart mandate standard GS1-compliant barcodes (UPC-A, EAN-13, or GTIN-14). This calculator generates and verifies the identical check digit required by their inventory receiving systems.
What is the difference between a check digit calculator and a barcode lookup?
A check digit calculator evaluates the mathematical structure and integrity of the digits. A barcode lookup (available on our GTIN Lookup page) queries commercial databases to identify product descriptions, brands, and photos matching that code.
Why does the check digit calculation alternate between weights of 3 and 1?
The alternating weights of 3 and 1 ensure that if two adjacent digits are accidentally transposed (for example, typing 78 instead of 87), the calculated sum will change. A simple unweighted sum would not detect transposition errors.
What should I do if my Amazon barcode is marked invalid?
First verify that the 12th digit matches the calculation above. If the check digit is correct, ensure your brand name on Amazon exactly matches the legal entity name registered in the GS1 database under your GS1 Company Prefix.