1. What is GS1 Check Digit?

The GS1 check digit is a single digit added to GS1 identification numbers (like GTINs used in barcodes) to ensure data integrity. It helps detect errors in scanning or manual entry of product codes.

2. How Does the Calculator Work?

The calculator uses the standard GS1 check digit formula:

Where:

• \( sum \) — Sum of weighted digits (odd positions from right multiplied by 3)
• \( \% \) — Modulo operation

Calculation Steps:

1. Start from the rightmost digit (excluding check digit)
2. Multiply digits in odd positions (from right) by 3
3. Multiply digits in even positions by 1
4. Sum all the results
5. Calculate check digit as (10 - (sum % 10)) % 10

3. Importance of Check Digit

Details: The check digit is crucial for error detection in barcode systems. It can catch about 90% of common data entry errors like single digit errors or transpositions.

4. Using the Calculator

Tips: Enter the GS1 digits without the check digit. The calculator will compute the correct check digit and show the complete number.

5. Frequently Asked Questions (FAQ)

Q1: What types of GS1 numbers use this check digit?
A: This algorithm is used for GTIN-8, GTIN-12 (UPC), GTIN-13 (EAN), and GTIN-14.

Q2: Can this calculator validate existing numbers?
A: Yes, enter all digits except the last one to verify if the calculated check digit matches the existing one.

Q3: Why is the weighting 3-1-3-1 etc.?
A: This alternating weight pattern helps detect transposition errors where adjacent digits are swapped.

Q4: What common errors does this detect?
A: Single digit errors, most adjacent digit transpositions, and some other common scanning errors.

Q5: Is this the same as ISBN check digits?
A: No, ISBN-10 and ISBN-13 use different check digit algorithms, though ISBN-13 uses the same as EAN-13.