1. What is GTIN Check Digit?

The GTIN (Global Trade Item Number) check digit is a single digit added to the end of a product barcode to ensure the number was correctly composed. It's used in various barcode standards including UPC, EAN, and ISBN-13.

2. How Does the Calculator Work?

The calculator uses the standard GTIN check digit formula:

Where:

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

Calculation Steps:

1. Take the first 12 digits of the GTIN
2. Multiply digits alternately by 1 and 3 (starting with 1 for first digit)
3. Sum all the multiplied values
4. Calculate the check digit that makes the total sum a multiple of 10

3. Importance of Check Digit

Details: The check digit helps prevent errors in barcode scanning and data entry. It's used to validate that the barcode number was correctly composed or transmitted.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What barcode types use this check digit method?
A: This method is used for GTIN-12 (UPC), GTIN-13 (EAN), GTIN-14, and ISBN-13.

Q2: Why are the weights 1 and 3?
A: The alternating weights help detect common errors like digit transpositions that might not be caught with equal weights.

Q3: What if my number already has a check digit?
A: You can verify it by calculating the check digit for the first 12 digits and comparing with the existing check digit.

Q4: Can this calculate ISBN-10 check digits?
A: No, ISBN-10 uses a different modulus 11 algorithm. This calculator is for GTIN standards.

Q5: What's the difference between GTIN and UPC?
A: UPC is a subset of GTIN. GTIN-12 is equivalent to UPC-A, while GTIN-13 is equivalent to EAN-13.