Every UPC Barcode Has 30 Bars
Virtually every product has a barcode on it. In North America, 12 digit UPCs are used. In Europe and parts of Asia, 13 digit EANs are the norm. Both systems are a unique set of numbers that represent that specific product. The numbers are printed for humans to read and represented as a barcode for computers to read.
The UPC (Universal Product Code) and EAN (European Article Number) are very similar; in fact, the EAN standard is heavily based on the 12 digit UPC standard.
The first UPC was scanned at a checkout in Troy, Ohio in 1974; it was a 10-pack of Wrigley’s Juicy Fruit gum. The UPC format is very well designed and hasn’t really changed since then.
All UPCs have 30 bars. Grab any product with a 12 digit UPC and count them. Some bars are thick and some thin, but there are 30 total. Thick bars are technically made up of a varying number of thin bars as you can see in the illustration below, but thick bars are only counted as a single bar for the purpose of this description.
Each of the 12 numbers accounts for 2 bars, which gives you 24 bars. Then there are 6 guard bars that give the scanner consistent reference points. There are 2 guard bars on each end and 2 in the middle for a total of 30 bars.
Each digit is represented by 2 black bars and white space of varying thickness. The guard bars in the middle divide the 12 digits into groups of 6. The same digit on the left and right sides will be represented differently by the bars, this allows the scanner to correctly identify upside down barcodes.
The first 8 digits refer to the company that registered the UPC. The next three digits uniquely identify the product.
The last digit in the sequence has nothing to do with the product itself, it’s called a check digit. It helps the computer identify a scanning error.
The check digit is a bit complicated, but here’s how it works. Add up the digits in the odd numbered positions (first, third, etc) and multiply by three. Next, add the digits in even positions to the first number, then find the remainder when divided by 10. If the remainder is not 0, then subtract the result from ten. That number should equal the last digit, if it doesn’t then the computer knows there was a scanning error and you get to scan your self-checkout item a fourth time.
There are some rumors that the first few digits can be used to identify the country of origin, but that’s not true. With 12 digit UPCs, no digits are used to identify a country. 13 digit EANs reserve the first three digits for country of registrar. This country code simply refers to the country where the code was registered and is in no way related to where the product is made.
Broken Secrets | Written By: Chad Upton
Images: Wikipedia (gnu)
Entry filed under: Demystified.