The UPC-A barcode is the most common and well-known symbology in North America. You can find it on the cartons of virtually every consumer goods in your local supermarket, as well as books, magazines, and newspapers. A short form is called UPC-E. Each symbol may have 2-digit or 5-digit supplement to encode additional information.

UPC-A encodes 11 digits of numeric data along with a trailing check digit, for a total of 12 digits of barcode data.

A UPC-A number consists of four elements: (1) the Number System; (2) the manufacturer code; (3) the product code; (4) the check digit. Normally the number system digit is printed to the left of the barcode, and the check digit to the right. The manufacturer and product codes are printed just below the barcode, separated by the guard bar.

The UPC-E barcode is the short form representation of a UPC number. It reduces the data length from 12 digits to 6 digits by compressing the extra zeros. It is suited for identifying products with small packages.

A UPC-E barcode has 6 digits with an implied number system 0. The first 5 digits are calculated based on a conversion algorithm described below. The last digit is the check digit of the original UPC-A symbol.

Both UPC-A and UPC-E symbols allow for a supplemental two- or five-digit add-on barcode. This add-on barcode usually encodes a price or a sequence number. To include a supplemental message, append it to the main message with a vertical bar (|) to separate it from the main message. The supplemental message must consist of exact two or five digits.