A barcode has a series of black bars of different widths with white spaces in between. These bars are printed on labels to help manufacturers and retailers identify, track and inventory any given product. All types of barcodes are read with a scanner that uses reflected light to interpret the code in the bars. The most standard and widely used barcodes are the Universal Product Code (UPC) and the European Article Numbering (EAN) barcodes. Before a barcode gets printed for labeling it is customary to check its accuracy. This can be accomplished by using a check digit calculator online.
Navigate to a website that offers a free check digit calculator such as BarcodeSolutions.com.au, GS1US.org or Barcode-US.com. These websites verify if a barcode is valid by matching its check digit, which is the last digit displayed on the barcode.
Enter the digits displayed below your barcode in the calculator that corresponds to the type of barcode you have. For instance, if your barcode has eight digits, use the EAN-8 or GTIN-8 calculator. The calculator will inform you how many digits to enter, usually one less than the total number of digits on the barcode.
Click the "Calculate" tab and the website will display a single digit (the Check Digit). If the single digit matches the the last digit on your barcode, the barcode is valid and ready for printing. However, if the check digit displayed on the computer and on your barcode are diferent, the barcode is not valid.