# UPC

A Universal Product Code (UPC) is a unique 12-digit number assigned to retail merchandise that identifies both the product and the vendor that sells the product. The UPC on a product is put in place by the manufacturer and typically appears adjacent to the item’s barcode, the machine-readable representation of the UPC. UPCs are widely used by many countries, including the United States, the European Union, Australia, New Zealand, and Canada.

## UPC check digit verification

The first six digits of the UPC are the vendor’s unique identification number. All of the products that one vendor sells will have the same first six digits in their UPCs. The next five digits are the product’s unique reference number that identifies the product within any one vendor’s line of products. The last number is called the check digit that is used to verify that the UPC for that specific product is correct.

The check digit verification works like this, using the UPC 438571639853 as an example:

1. The digits in the odd positions are added together: 4 + 8 + 7 + 6 + 9 + 5 = 39
2. That number is multiplied by 3: 39 x 3 = 117
3. The digits in the even positions (except for the 12th digit) are added together: 3 + 5 + 1 + 3 + 8 = 20
4. This sum is added to the value in step 2: 117 + 20 = 137
5. The check digit is the number that when added to that sum (137) equals a multiple of 10: 137 + 3 = 140, therefore the check digit for the above UPC is 3, which appears as the last digit of the UPC.

Each time that a UPC is read, typically by a scanner reading the barcode, this calculation is done. If the check digit is different from the one that is calculated, then the computer knows that there is something wrong with the UPC.

## UPC vs. SKU

Unlike manufacturer-printed UPCs that are standardized regardless of retailer, stock keeping units (SKUs) depend on the individual store that is selling the manufacturer’s product. They are designated by the retailer and used to keep track of inventory. Many retailers use the item’s UPC as its SKU for simplicity, but sometimes the SKU will be different if the manufacturer has changed the UPC for an item after it has been received by the retailer.

## How to get a UPC code

Anyone wishing to use the UPC system must first apply for rights through GS1 (formerly the Uniform Code Council), the international organization responsible for administering UPCs and other standards. GS1 approves the company prefix, a 6-9 digit code that will be used in every UPC the manufacturer creates. Then the manufacturer creates a number for each unique product so that the code 11 digits and generates a check digit using the steps above to create the full 12-digit UPC.