UPC-A barcode symbology

UPC-A

UPC-A is linear barcode symbology of the EAN/UPC Symbology family. UPC is short for Universal Product Code which widely used for retailing industry to track Global Trade Item Numbers (GTIN) since 1970s. UPC-A was used to encode UPC-A encodes the EAN/UPC barcodes like GTIN-12, Coupon-12, RCN-12, and VMN-12. UPC-A is an subset of EAN-13. It usually composed of 12 numerical digits. Based on GS1 standards, UPC-A is the only barcode which could be used for scanning trade items in point of sale industry. The barcode shows details of the manufacturer and specific product. UPC-A is easy to be found on books, CDs and newspapers.

Structure of the UPC-A

The UPC-A barcode is composed of 4 parts, the number system to identify the type of the product, the manufacturer code uniquely assigned by UCC council, the product code and the checksum digit. The structure of UPC-A barcode showed as below represented as black bars and white spaces:

A left Quiet Zone. The number system digit is encoded to the left of the barcode
A normal Guard Bar Pattern
Six symbol characters from number set A
A centre Guard Bar Pattern
Six symbol characters from number set C
A normal Guard Bar Pattern
A right Quiet Zone. The checksum digit is encoded to the right side of the barcode.

In most of the cases, UPC-A barcodes encodes 12 numerical digits. These 12 digits are divided into 2 parts, each with 6 digits. The right-hand side of the first digit is positioned five module widths to the leftmost guard bar. Those numerical digits are assigned to the trade item. And A two-digit Add-On Symbol or five-digit Add-On Symbol may be used in an UPC-A barcode. Thus UPC-A supplement 2 (2-digit Add-on) or UPC-A suppliemnt 5 (5-digit Add-on) is obtained. The add-on digit symbol should be appended following the right Quiet Zone of UPC-A barcode.

Encoded Data of UPC-A

UPC-A encodes 11 digits of numeric numbers: 0~9

Plus the checksum digit, the total length is 12 digits long.

Checksum Digit of UPC-A

The checksum digit is essential to offer detection for scanning the barcode. Like EAN-13, the checksum digit is calculated based on the Mod10 standards. The Mod10 method is utilized for verification of barcode as: PC-A, UPC-E, EAN-13 and EAN-8.
Just follow the steps:

Choose the right most digits as the odd digit, and put it into the right most column below.
Assigned the following digits from right to left in sequence into the odd and even position.
Multiple all value in odd position with 3. Multiple all value in even position with 1.
Sum up all the result.
Put an number to add with the result and let it be even divided by 10.
The number added is the checksum digit. Like in the example, (8) +102=110. Number 8 helps number 102 to be even divided by 10. 8 is the checksum digit of the UPC-A barcode.

For example, the checksum digit is calculated as below if we encode "2345678912"

3+ 2 + 9 + 4 + 15 + 6 +21 +8 + 27 +1 + 6 = 102

We need to add No. 8 to 105, and it could be even divided by 10. (8)+102=110.

Note: If the result could be even divided by 10, like 100, the check digit is 0.

The checksum digit of "2345678912" is 8, the barcode ITF-14 generated is "23456789128"

UPC-A Symbology