A GTIN that is assigned for an individual sale unit has 12 digits and is called a GTIN-12. This allows it to be carried in a UPC-A barcode, the usual barcode that is scanned at point-of-sale in North America. A GTIN that is assigned for a higher-level grouping such as a homogeneous case, homogeneous pallet, etc., has 14 digits and is called a GTIN-14. The first digit of such a GTIN is a digit between and 8 (inclusive) and is called the indicator digit. These are the two lengths of GTIN that are used for U.S. pharmaceuticals, where the NDC is embedded in the GTIN. (There are also 8-digit and 13-digit GTINs that are used for individual sale units, primarily by non-U.S. manufacturers, but a GTIN that embeds an NDC code is never a GTIN-8 or GTIN-13.

However, when a GTIN is carried in a GS1-128, GS1 DataMatrix, GS1 DataBar®, or GS1 QR barcode, it is always represented as 14 digits. A GTIN-12 is padded by adding two zero digits to the left to make 14 digits, when it is carried in these barcodes. The same is true when GTINs are stored in databases: both GTIN-12 and GTIN-14 are stored as 14 digits, with the GTIN-12 padded on the left with two zero digits. The only context in which a GTIN-12 appears as only 12 digits is in a UPC-A barcode. For this reason, it is easiest to think of a GTIN as always having 14 digits, even though for an individual sale unit it is really 12 digits preceded by two zero “filler” digits.