1. What is a GTIN Check Digit?

A GTIN (Global Trade Item Number) check digit is the final digit in a GTIN (including UPC, EAN, and ISBN-13) that validates the entire number. It's calculated from the other digits to ensure data integrity during scanning or manual entry.

2. How the Check Digit is Calculated

The calculator uses the GS1 standard formula:

Calculation Steps:

1. Start with the number without its check digit
2. Multiply each digit by 3 or 1 alternately, starting with 3 for the first digit
3. Sum all the multiplied digits
4. Find the number that makes the sum a multiple of 10

3. Importance of Check Digits

Details: Check digits help detect common data entry errors like single-digit errors, transposition errors, and phonetic errors. They are critical for barcode scanning reliability in retail and inventory systems.

4. Using the Calculator

Tips: Enter the GTIN number without its final check digit (7-17 digits). The calculator will compute the correct check digit and display the complete GTIN.

5. Frequently Asked Questions (FAQ)

Q1: What GTIN formats does this work for?
A: This works for all GS1 GTIN formats including UPC-A (12-digit), UPC-E (8-digit), EAN-13 (13-digit), and EAN-8 (8-digit).

Q2: Why does the formula alternate between 3 and 1?
A: The alternating weights help detect transposition errors where adjacent digits are swapped.

Q3: Can this validate an existing GTIN?
A: Yes, you can enter all digits except the last one to see if the calculated check digit matches the existing one.

Q4: What's the difference between GTIN and UPC?
A: UPC is a specific type of GTIN (12 digits). GTIN is the broader standard that includes various formats.

Q5: Are there other check digit algorithms?
A: Yes, different systems use different algorithms (like Luhn for credit cards), but this is the standard for GTINs.