A UPC is the familiar Universal Price Code that appears beneath bar codes on American consumer products. A GTIN is a Global Trade Item Number, which is administered by the European Article Numbering-Uniform Code Council (EAN-UCC). A UPC is either a standard, 12-digit UPC-A or an 8-digit UPC-E. A simple process is used to convert either type of UPC to a GTIN by adding zeroes to pad the number.
Write down the UPC. For example, 036121163003 is the 12-digit UPC-A from a bottle of Finish Line Cross Country Synthetic Bicycle Lubricant. 01801624 is the 8-digit UPC-E from a 12-oz. can of Budweiser beer.
Add two leading zeroes to the UPC-A to obtain a 14-digit GTIN. The GTIN for the bottle of bicycle lubricant is then 00036121163003.
Add six leading zeroes to the UPC-E to obtain a 14-digit GTIN. The GTIN for the can of beer is then 00000001801624.