1. What is GTIN?

GTIN (Global Trade Item Number) is a unique identifier for trade items developed by GS1. It includes UPC (12-digit), EAN (13-digit), and other formats. The last digit is a check digit calculated from the preceding digits.

2. How Does the Check Digit Calculation Work?

The calculator uses the standard GTIN check digit formula:

Where:

• \( sum \) — Sum of digits with alternating weights of 3 and 1
• \( \mod \) — Modulo operation (remainder after division)

Explanation: Starting from the right (excluding check digit), multiply digits alternately by 3 and 1, sum them, then calculate the check digit that makes the total sum a multiple of 10.

3. Importance of GTIN Check Digit

Details: The check digit ensures data integrity by detecting common errors in GTIN entry or transmission (single-digit errors, most transpositions).

4. Using the Calculator

Tips: Enter the first 7 digits for GTIN-8, 11 for GTIN-12, 12 for GTIN-13, or 14 for GTIN-14. The calculator will compute the check digit and display the complete GTIN.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between GTIN, UPC, and EAN?
A: UPC is a 12-digit GTIN used primarily in North America. EAN is a 13-digit GTIN used internationally. All are part of the GTIN system.

Q2: Why does the weighting alternate between 3 and 1?
A: This pattern helps detect transposition errors (swapped adjacent digits) which account for about 10-20% of all errors.

Q3: Can this calculator validate existing GTINs?
A: Yes, enter all digits except the last one to verify if the calculated check digit matches the existing one.

Q4: What common errors does the check digit catch?
A: It detects all single-digit errors and about 89% of transposition errors.

Q5: Are there GTINs that don't use this check digit?
A: No, all standard GTIN formats (GTIN-8, GTIN-12, GTIN-13, GTIN-14) use this same check digit calculation method.