UPC Codes: What They Are and How They Work

Curious about How UPCs Work? Get the Answers Here

Close up of bar codes, studio shot
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What Is a UPC Barcode? The Definition:

A UPC code is a symbol used by manufacturers to identify their products quickly. UPC stands for "Universal Product Code." UPC codes make it easy to ring up products at a grocery store, track inventory, reorder stock that is running low, print receipts that show the products you bought, make coupons scannable, and many other useful things.

Although there are other bar code systems, UPCs are the most commonly-used tracking system in United States, Canada, and many other countries.

Also Known As: Universal Product Code, Bar Code, UPC Bar Code

Examples: To enter, you'll need a UPC Code from a specially-marked package of Diet Coke.

How UPC Codes Work:

A UPC code is made up of two ways of displaying a 12-digit number:

  1. A bar code:
    The bar code is designed to be easily read by computer scanners. It consists of bars of various widths. Each numeral from zero to nine corresponds to a pattern of bars of various length, alternating between the two colors.

    For example, a one would be written as three bars each two lengths wide followed by a bar one length wide. Remember that you need to consider both the white and black bars when deciphering the code.

    The bar code starts and ends with a black bar, a white bar, and a black bar, each one unit in width. (These are called the start code and the end code, respectively). Between the start and end codes, you'll find the bars indicating the numbers in the code.
  1. A 12-digit number:
    The plain-text version of the number is printed so that humans can read it easily. This is useful, for example, if a scanner isn't working properly; a cashier can simply type in the number, whereas deciphering the bars is difficult with the native eye.

Why Do UPC Codes Have 12 Numbers?

The 12-digit UPC number is actually made up of groups of numbers with different purposes.

In a product UPC, the first six numbers indicate the manufacturer. The next five digits are an item number, and the final number is the check digit.

(Coupons also have UPC codes, and can be scanned to check whether the coupon is being used with the right product, to track when and where coupons are being used, and to verify that the coupon is still valid. Coupon UPCs start with the digit 5. Read more from the Couponing Expert: How to Read Coupon UPCs.)

Each manufacturer needs to assign an item number for each individual product. For example, the item numbers for a 6-pack of strawberry yogurt, a single container of strawberry yogurt, and single blueberry yogurt from the same manufacturer would all be different.

The check digit is added to help ensure that the right number has been scanned or hand-entered. It works by adding up all of the odd digits in the code and multiplying the result by three, then adding up all of the even digits. The amount you would need to add to the result to reach a multiple of ten should match the check digit. If not, something has gone wrong.

Why Are UPCs Sometimes Shorter Than 12 Digits?

In order to be able to print UPC bar codes on smaller packages, there is a way of compressing the zeros in a UPC to save space.

You can read more about zero-compressed numbers from How Things Work.

What Is Not Included in UPC Codes:

A UPC Code does not carry any price information. When the code is scanned, a store's computer will check that product against the current price stored in its database to determine the cost of that product. Otherwise, a new UPC code would have to be printed every time a price was changed (and the manufacturer would also have to know the price the stores wanted to set. That would be a nightmare to track!)

As the Urban Legends Expert explains, UPC codes also don't carry information about where a product was manufactured, despite various viral emails and social media posts claiming otherwise.

UPC Codes and Sweepstakes

Companies sometimes require a UPC Code from one of their products in order to enter sweepstakes.

However, this does not mean you have to buy the product to enter (remember that it's not generally legal to require a purchase to enter a randomly-drawn sweepstakes, and here's why).

See How to Find Free UPC Codes for more information about entering these kinds of sweepstakes without purchase.