The upc-a (Universal Product Code - A) bar code type represents a 12-digit decimal number assigned to a trade item.

First digit is the 'number system character' code, the next five identify the manufacturer and the following five identify an article. The last digit is the check character. The check character is calculated the same way as the ean 13 check sum.

The rightmost digit (checksum digit) can be omitted. When the system is supplied with such a 11 digit value then the 12th digit is automatically calculated by the system.

The nominal size is 1.469in x 1.020in (w x h). The bar code area has the measurements 1.235in x 0.965in. The left padding measures 0.117in.