Every UPC Barcode Has 30 Bars
April 30, 2010 at 12:37 am Chad Upton 7 comments
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.
UPCs are registered with a non-profit organization called GS1. There is also a website for looking up UPCs, called the UPC database. It can be searched by UPC or by product description.
Broken Secrets | Written By: Chad Upton
Sources: UPCs, EANs, About.com
Images: Wikipedia (gnu)
Entry filed under: Demystified.
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1.
Charyl | April 30, 2010 at 11:10 am
Very interesting, can you also explain to consumers that a sku is very different from a UPC
2.
Casey | May 7, 2010 at 1:00 pm
The part about the first 8 digits identifying the company isn’t quite correct. It all depends how much you want to pay. For us the first 9 digits identify us which leaves us with 2 digits and 100 possible bar codes, since that was all we needed and it was quite a bit cheaper.
3.
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4.
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5.
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6.
Chuck Somerville | July 11, 2012 at 9:34 pm
Actually, EAN-13 and UPC “12” are the same, in that they contain the same number of bars (30) consisting of start, middle, and end “guard bars”, and six 2-bar-and-2-space number characters on each side of the middle guard bars. There are three 10-digit sets of bar code characters, the left side “A” character set, the left side “B” character set, and the right side “C” character set (inverse images of the A set characters). The left side B characters are simply a different character set to represent 10 digits (and are not used in UPCA 12-digit bar codes. The left-side six digits can be represented by a combination of A and B characters, and the pattern of A and B characters represents a 13th digit (at the left end of the number). All six left side digits being “A” characters makes the 13th digit a zero, and so any UPC is really an EAN-13 bar code with the left-most digit being zero (which is not printed in the human readable text under the bar code in the USA) and the left-hand first two or three digits, which are the country code, begin with zero, and all country codes beginning with zero are reserved for the USA. UPC originated in Dayton Ohio USA (where I am). (Kind of like the telephone country codes – where 1 is USA, since we invented the telephone.)
7.
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