How to Read a Barcode - Wholesale Distribution of America

To read a barcode (Bar Code), first, lets analyze what we see. You can read the barcode numbers. In the United States, barcodes are universally standardized, with the major exceptions being Walmart and Kroger, which employ other proprietary systems. There is a variety of barcode standards. Most commonly, bar codes are 12-digit UPC (Universal Product Code) barcodes, with ten digits at the bottom of the graphic code, conforming to the GTIN (Global Trade Identification Number) data structures. There is, most often, one small numeral located each side of the main numeral set of the barcode.

Outside of the United States and Canada, we most often see a similar barcode system, the 13-digit EAN barcode system, which utilizes an additional digit, which is part of a designated country code. Obviously, the very best way to read a barcode is with a barcode scanning device, which will return a text identifier. However, the GTIN-12, which consists of twelve numeric characters that uniquely identify a company's individual product is the common North American standard.

Note: As of early in 2005, there were significant changes made to the accepted terminology involving product barcode marking. You can visit www.gtin.info to learn more about this new GTIN (Global Trade Identification Number) data structure standard.

First, a few basics in reading a barcode:

Most common barcodes, having fewer than 12 digits, the 'white/black/white/black' scheme.

Barcode line colors are reversed after the center line: The lines of the digits to the left are white/black/white/black whilst to the right they are black/white/black/white. This provides some error checking and allows the reader to know the direction in which it is scanning a code. It is also crucial so that the barcode ends with a bar rather than a space. So, actually, each digit has two codes.

In the most commonly used barcode system the first code delineates the actual product manufacturer, regardless of what you might see on the labeling.

The vertical barcode lines are differing widths.

The barcode is split into two halves of six digits each. The first digit most always zero, except products that have variable weight, etc. The next five are the manufacturer's code. The next five are the product code, and the last is a "check digit" that is used to verify that the preceding digits have been scanned properly. Hidden cues in the structure of the code tell the scanner which end is which, so it can be scanned in any direction. Manufacturers register with the UCC (Uniform Code Council ) to get a unique identifier code for their company and each product. Each bar-coded product passing over a checkout scanner has a unique ID number.

There are four different thicknesses to the lines. For the purposes of this article, we will identify each with letters with the thinnest referred to as "1," the next thickest line as "2," the next thickness of lines as "3." and the thickest line as a "4."

The US-used UPC barcode begins and ends with 101, in lines that is, thin black, thin white, thin black. In the middle of the graphic barcode, you will notice two thin black lines sticking down between the numbers. The thin white space between them, as well as the thin white spaces on either side, make up a 01010. Every UPC barcode has 01010 in the middle.

In analysis, we see that each 'digit' of a barcode, including the small numbers at the beginning and end of every barcode, has a unique four-line grouping to represent a unique 10-based numeral. That is: 0 = 3211; 1 = 2221; 2 = 2122; 3 = 1411; 4 = 1132; 5 = 1231; 6 = 1114; 7 = 1312; 8 = 1213, and; 9 = 3112. Notice that the sum of bar width numbers is 7 for all codes because each of the codes is 7 units wide. Notice that each graphic 'digit' is made up of seven lines, spaced equally.