The data encoded inside a UPC barcode is known as the GTIN-12. GS1 is the global identification standards organization who created the Global Trade Item Number (GTIN) data structures. GTIN-12 is used to represent UPC barcodes in the United States. As referenced below, the GTIN-12 is an identifier consisting three components.


U.P.C. Company Prefix

The first portion of a GTIN-12 (UPC) code is the UPC Company Prefix. A UPC Company Prefix is a 6 – 10 digit number assigned to members by the GS1 organization in the United States.  The number of digits in a Company Prefix can vary between 6 – 10 characters, depending on the number of products a manufacturer needs to identify. A small company, who only needs to identify 1 – 10 products, would receive a 10-digit number. The membership fee for GS1 US is primarily based on the number of products that require identification. As of November 2020, GS1 has begun offering single GS1 US UPC GTIN identifiers to accommodate the needs of small companies that only need a few UPCs for product identification. These single UPCs do not have separate Company Prefix, BUT the brand and product description will be designated in the GS1 Global Registry. To learn more, please visit www.barcode-us.com/.

Item Reference Number

The UPC Company Prefix and Item Reference Number must always total 11-digits.   The amount of digits of an Item Reference number is dependent on the length of the UPC Company Prefix assigned. The GS1 takes into account the number of prospective products your company plans on selling when assigning a UPC Company.  For companies which sell many different items and need to assign more UPC (GTIN-12) numbers will receive a shorter prefix, allowing them to assign a larger range of digits for their products, while companies needing less UPC (GTIN-12) numbers will be assigned a longer UPC Company Prefix which will reduce the number of UPC (GTIN-12) numbers that can be assigned.

For organizations with a 6-digit Company Prefix, a 5-digit product number must be created. Companies with a 9-digit Company Prefix can only create a 2-digit number. A unique Item Reference number is needed for each variety of item being sold.  For example, let’s say you’re selling t-shirts in two different styles – yellow and blue. The blue small, medium and large t-shirts would each have their own unique product numbers, while the yellow small, medium and large t-shirts would also have their own different unique product numbers.

GTIN-12 item numberGTIN-12 example.

Product Style Item Reference Number Full UPC (GTIN-12) Number
Blue Shirt – Small 1 01234500001-0
Blue Shirt – Medium 2 01234500002-7
Blue Shirt – Large 3 01234500003-4
Orange Shirt – Small 4 01234500004-1
Orange Shirt – Medium 5 01234500005-8
Orange Shirt – Large 6 01234500006-5

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Check Digit

The 12th digit of a GTIN-12 is a calculated digit based on a MOD check digit calculation from the 11 preceding digits. The check digit prevents substitution error, which would result if one digit read as another. It would be better for a barcode to not scan at all than to scan as an incorrect product.

To calculate a GTIN-12 check digit CALCULATE

To manually calculate the check digit using modulo algorithm, follow these 5 steps;
Example: If the first 11 digits of GTIN-12 is; 01234567890

Step 1:

Add all of the ODD positions (1,3,5,7,9,11)

Step 2:

Multiply value from Step 1 by 3

Step 3:

Add all of the EVEN positions (2,4,6,8,10)

Step 4:

Add value from STEP 2 and STEP 3 together

Step 5:

Determine what number is needed to make value from STEP 4 into a multiple of 10.

Example 1:

Odd positions equals; 20 (0+2+4+6+8+0)

Example 2:

Multiply 20 x 3 = 60

Example 3:

Even positions equals: 25  (1+3+5+7+9)

Example 4:

STEP 2 and STEP 3 equals: 85 (60+25)

Example 5:

Check Digit is 5 (85+ 5 = 90)

Creating & Printing UPC Barcodes

Verifying UPC Barcodes