UPC, EAN and GTIN: what the barcode numbers mean

The number under a barcode is a product identifier. You will see it called a UPC, an EAN or a GTIN, and they are closely related.

GTIN is the umbrella term

GTIN stands for Global Trade Item Number. UPC and EAN are two common formats of it, which come in different lengths:

• UPC-A has 12 digits and is the common format on products sold in North America.
• EAN-13 has 13 digits and is used worldwide.
• EAN-8 has 8 digits and is used on small packages with little room for a long code.
• GTIN-14 has 14 digits and is generally used to identify a case or carton of items rather than one item.

A UPC-A is an EAN-13 with a leading zero

Add a zero in front of a 12-digit UPC-A and you have the equivalent 13-digit EAN-13. For example, the UPC-A 036000291452 is the EAN-13 0036000291452. If a search by one form finds nothing, try the other.

The last digit is a check digit

The final digit is calculated from the others, so a mistyped number is usually caught. Work from the digit next to the check digit and move left, multiplying alternately by 3 and 1, then add up the results. The check digit brings the total up to the next multiple of 10.

Take 03600029145, which is the UPC-A above without its last digit. From the right the digits are 5, 4, 1, 9, 2, 0, 0, 0, 6, 3, 0, and multiplying them by 3, 1, 3, 1 and so on gives 15, 4, 3, 9, 6, 0, 0, 0, 18, 3, 0. They add up to 58. The next multiple of 10 is 60, so the check digit is 2, and the full number is 036000291452.

What a correct check digit does not tell you

A correct check digit means the number is well formed. It does not prove the barcode belongs to a real product, and it does not tell you which product it is. Different pack sizes and regional versions of the same product usually have different barcodes, so two barcodes for what looks like the same thing can both be right.

When a barcode search finds nothing

• Check the digits against the check-digit rule above, in case one was mistyped.
• Try the UPC-A and EAN-13 forms of the number.
• Confirm you copied the number under the barcode, and not a batch or serial number printed nearby.
• Remember that a valid number can still be missing from a given catalog.

The barcode check-digit checker does the arithmetic for you and shows the UPC-A and EAN-13 forms side by side.