1. What is GS1 Check Digit?

The GS1 check digit is the 13th digit in a GTIN (Global Trade Item Number) that validates the previous 12 digits. It's used in barcodes (UPC, EAN) to ensure data integrity during scanning.

2. How Does the Calculator Work?

The calculator uses the GS1 check digit formula:

Where:

• \( sum \) — Sum of weighted digits (odd positions ×1, even positions ×3)
• \( \mod 10 \) — Remainder after division by 10

Calculation Steps:

1. Multiply digits in odd positions (1st, 3rd, etc.) by 1
2. Multiply digits in even positions (2nd, 4th, etc.) by 3
3. Sum all these weighted values
4. Find the remainder when divided by 10
5. Subtract from 10 (or 0 if remainder is 0)

3. Importance of Check Digit

Details: The check digit helps detect common scanning errors like single digit errors or transposition errors. It's crucial for retail, inventory management, and supply chain operations.

4. Using the Calculator

Tips: Enter the first 12 digits of your GTIN (without the check digit). The calculator will compute the correct 13th digit and display the complete GTIN.

5. Frequently Asked Questions (FAQ)

Q1: What types of barcodes use this check digit?
A: UPC-A, EAN-13, and other GS1-128 barcodes all use this calculation method.

Q2: Why are positions weighted differently?
A: The 1-3-1 weighting pattern helps detect transposition errors where adjacent digits are swapped.

Q3: What if my number has fewer than 12 digits?
A: For shorter numbers (like UPC-E), pad with leading zeros to make 12 digits before calculation.

Q4: Can this verify existing barcodes?
A: Yes, calculate the check digit from the first 12 digits and compare with the 13th digit.

Q5: Are there other check digit algorithms?
A: Yes, different systems use different algorithms (ISBN uses modulo 11, for example).