UPC-A barcodes have 12 digits.
First digit is UPC code type (number system). Next five is manufacturer number. The next five is product number. Last digit is calculated check-digit.
This barcode generator accepts either 11 or 12 digits and prints either 10 or 12 digits below the UCP image. If 11 digits are passed to the generator then the 12th (check-digit) will be automagically added. If 12 digits are passed then that 12th digit will be validated to be the correct check-digit for the first 11 digits. The display of the outer 2 digits in the human readable text below the barcode can be enabled or disabled depending on the 'display_outer_digits' value in the options hash passed to the constructor (defaults to true). All 12 digits are always reflected in the barcode graphic.
Based on original work by rexfeng: http://cssdeck.com/labs/css-barcode-upc-a-generator
You entered . The checksum digit was . Your barcode above is encoded as .