UPC-A barcode generator

Twelve digits — eleven plus a check digit. UPC-A is the North American retail standard and is, structurally, an EAN-13 whose first digit is zero.

That relationship is why a European scanner reads a US product without modification: the bar pattern is identical, and the leading zero is implied rather than printed. It also means a UPC-A can be written as an EAN-13 by prefixing a zero, which is what most databases store. The first digit of the printed number is the number system character, and its values are meaningful — 0, 6, 7 and 8 are general retail, 2 is variable-weight items priced at the store, 3 is pharmaceutical, and 5 is coupons. A variable-weight code carries the price in the digits, which is why deli labels look like barcodes with prices in them.