What UPC Codes Are and How They Work

Curious How UPCs Work? Get the Answers Here

Close up of bar codes, studio shot
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Some contests and sweepstakes require you to enter a product UPC code to complete your entry. But what are UPCs? Where can you find them? And do you have to buy a product to enter this kind of giveaway? Here's everything you need to know about UPC barcodes and sweepstakes.

What Is the Definition of a UPC Barcode?

UPC stands for "Universal Product Code." UPCs are barcode symbols that manufacturers use to identify their products electronically. The codes enable those products to be digitally scanned and tracked.


Because of what the abbreviation stands for, when you say "UPC Code," you're actually saying "Universal Product Code Code." Technically, it's more correct to say just "UPC" instead of tacking the second code onto the end. However, if UPC Code sounds better to you, feel free to keep using it. Just be aware that some pedantic people might point out the duplication!

Each UPC consists of a series of digitally readable bars, along with printed numbers that people can verify.

UPC codes are used to ring up products at a grocery store, track inventory, reorder stock, print detailed receipts, make coupons scannable by computers, and so on.

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

How UPCs Work

A UPC code is a 12 digit code that's unique to a specific product. It's displayed in two different ways: a barcode and printed numbers.

The barcode is designed for computer scanners to easily read. It consists of alternating white and black bars of various widths. Each numeral from zero to nine corresponds to a specific pattern of bars.

For example, the number 1 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 UPC series 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. Between the start and end codes, you'll find the bars indicating the numbers in the code.

The second part of a UPC code is a plain-text version of the number, which is printed near the barcode so that humans can read it easily. This lets the cashier enter the code by hand if the scanner isn't working, for example. The plaintext number is faster for the cashier to type than trying to decipher the code would be, and having it there reduces the chance of making a mistake when keying in the product information by hand.

Why Do UPC Codes Have 12 Numbers?

The 12-digit UPC code consists of three groups of numbers with different purposes. In a product UPC, the first 6 numbers indicate the manufacturer, the next 5 digits are the item number, and the final number is the check digit.

The manufacturer's section of the UPC is technically called the UPC Company Prefix. It's assigned to the manufacturer when they apply for a UPC barcode. Every item that the manufacturer sells will start with this number.

The second group of numbers — the item number — is assigned to each individual product by the manufacturer. For example, the item numbers for a six-pack of strawberry yogurt, a single container of strawberry yogurt, and a single blueberry yogurt from the same manufacturer would all be different from one another.

The check digit is there to ensure that the right number has been scanned or hand-entered. To check whether the correct numbers are in the code, add up all the odd digits in the code and multiply the result by three. Then add up all of the even digits and add them to the result. The amount you'd need to add to that amount to reach a multiple of ten should match the check digit. If not, something has gone wrong. If that seems complicated, you can also use a checksum calculator to verify your UPC without having to do a lot of math.

Coupons can also have UPC codes. Scanning them checks if the coupon is being used with the right product, tracks when and where the coupons are being used, and verifies whether the coupon is still valid. Coupon UPCs generally start with the digit "5."

Why Are UPCs Sometimes Shorter Than 12 Digits?

A 12-digit UPC is hard to print on a small package. To solve this problem, manufacturers compress the zeros in a UPC to save space, resulting in barcodes that have less than 12 digits. You can read more about zero-compressed numbers from How Things Work.

What Isn't Included in UPC Codes

A UPC Code doesn't 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 the product. Otherwise, a new UPC code would have to be printed every time a price changes, and the manufacturer would also have to know the price the stores wanted to set. That would be a nightmare to track!

UPC codes also don't carry information about where a product was manufactured, despite various viral emails and social media posts claiming otherwise. You can't look at certain numbers of a UPC code and determine that the product was made in China or other countries. EIN numbers, which are commonly used in Europe, might contain this information.

UPC Codes and Sweepstakes

Companies sometimes require a UPC Code from one of their products to enter sweepstakes. However, this does not mean you have to buy the product to enter. It's generally illegal to require a purchase to enter randomly-drawn sweepstakes, and here's why

There are several ways to enter these sweepstakes without having to buy anything. See How to Find Free UPC Codes for more information about entering these kinds of sweepstakes without purchase.