GTIN Check Digit Calculator

Understanding GTIN and GS1 Check Digits

A Global Trade Item Number (GTIN) is a unique international identifier used to identify trade items, products, or services. Standard barcode formats—including GTIN-8, GTIN-12 (UPC-A), GTIN-13 (EAN-13), GTIN-14, and SSCC-18—all rely on a final single-digit check digit to ensure data integrity and prevent scanning errors.

The GS1 Check Digit Calculation Algorithm

The official GS1 algorithm computes the check digit using a modulo 10 weighted sum. Starting from the rightmost payload digit and moving leftward, digits are multiplied by alternating weights of 3 and 1.

Step-by-step formula:

$$\text{Weighted Sum} = \sum_{i=1}^{n} (\text{Digit}_i \times \text{Weight}_i)$$

$$\text{Check Digit} = (10 - (\text{Weighted Sum} \pmod{10})) \pmod{10}$$

Supported Barcode Standards

• GTIN-12 (UPC-A): 11 data digits + 1 check digit (used primarily in North America).
• GTIN-13 (EAN-13): 12 data digits + 1 check digit (used worldwide for retail products).
• GTIN-8: 7 data digits + 1 check digit (used on small retail items).
• GTIN-14: 13 data digits + 1 check digit (used for wholesale cartons and cases).
• SSCC: 17 data digits + 1 check digit (Serial Shipping Container Code for logistics).