 # Barcoding

December 15, 2014

How Barcoding Works

As inventory automation software experts, we make extensive use of barcodes here at HandiFox, but for many of our customers, the mechanics of barcoding remains a mystery. So for this blog, we’re going to take a look at exactly how barcodes work.

UPC Barcodes

Most barcodes are UPC barcodes - these are the codes composed of vertical lines that can be found on virtually everything from auto parts to a carton of milk. UPC stands for Universal Product Code, and these codes originate from a company called the Universal Code Council (UCC). The UPC symbol is actually composed of two parts – the machine readable bar code, composed of vertical lines of varying thickness, and the human readable UPC, composed of cardinal numbers. These two components actually have the same data, just represented in different forms.

The number itself has two sections. The first six digits represent the manufacturer identification number, and the next five digits represent the item number. Finally, the last digit in the UPC number is called a check digit, which ensures that the code has been scanned correctly. Here’s how the check digit is calculated (it gets a little complicated!):

Let’s start with an imaginary UPC of 1 - 23456 – 78909 - 8

1. Add the value of every digit in an odd position in the UPC (i.e. digits 1, 3, 5, 7, 9, & 11) = 34
2. Multiply that number by 3. 34 * 3 = 102
3. Add the value of every digit in an even position in the UPC (i.e. digits 2, 4, 6, 8, & 10) = 20
4. Add this sum to the value from step 2. 102 + 2 = 122
5. To create the check digit, determine the number that, when added to the value from step for, produces a multiple of 10. 122 + 8 = 130.

So our check digit, in this example, would be 8.