How is the check digit calculated?
When you calculate the check digit you always use the first 11 digits of the 12 digit UPC-A formatted code or the first 12 digits of the EAN-13 formatted code. The UPC-E code must first be in the 12 digit UPC-A format before the check digit can be calculated. So if you are trying to calculate the check digit of a UPC-E code, you must restore the code to the UPC-A format first. Many scanners do this automatically for you if you want. They always do this in order to check the check digit but they don’t automatically send the 12 digit version to the computer unless programmed to do so. For our example, we will use the code shown in the picture above and walk through the process one step at a time. The full 12 digit UPC-A code for the image above is 064200115896. Remember, the last digit is the check digit so when we calculate our own check digit we only use the first 11 digits. When done we will compare it to the scanned digit 6 and make sure they match.
