Although barcodes are designed to be "read" by scanners and interpreted by computers, it is possible with practice to look at a UPC barcode and translate it into a 12-digit number. This is rarely useful, especially since the 12 digits are usually printed beneath the bars, but you could learn it as a neat trick to show your friends or coworkers. Barcodes using non-UPC systems or different numbers of digits cannot be read using this method. Most barcodes on products sold in the U.S. and Canada are UPC barcodes, but be wary of compressed 6-digit UPC barcodes, which have a different, more complex encoding system. The barcode should be divided into three sections by sets of slightly longer lines. Look at the bottom of the vertical bars: some of the lines should extend further down than the others. There should be two longer lines at the beginning, two in the middle, and two at the end. These are there to help a barcode scanning machine read the bar code, and do not get interpreted as numbers. However, they still have a purpose in this method: the bars to the left of the central longer lines get read slightly differently than the bars on the right. This is explained in detail below. Each vertical bar (black or white) can have one of four different widths. Going from thinnest to thickest, these will be described as widths 1, 2, 3, or 4 for the rest of this method. Using a magnifying glass if necessary, try to figure out the differences in the line widths. Telling the difference between two lines of similar widths can be the hardest part of reading a bar code. Don't confuse this for the actual numbers you're trying to find, the numbers 1 through 4 only describe the width of the bars. Start with the bars on the left hand side, between the longer bars on the left and the longer bars in the center. Begin with the first white bar on the left hand side, and measure the thickness of each bar, black and white. Each digit in the 12-digit number you're trying to find is encoded using four bars. Write down the thickness of each bar, dividing them into four-bar groups. When you reach the extra-long center bars, you'll have six groups of four digits each.  For example, if the first white bar after the extra-long lines on the left hand side is the thinnest size, write down 1. Next, if the black bar to the right is the thickest size, write down 4. Once you've done this for four bars (black and white), leave a space before writing down the next bar. For example, once you've written down "1422," move your pen to a new line before writing down the next bar width. Do not decode the extra-long bars in the center. Starting with the first normal-length black bar to the right of them, use the same technique. This time, each group of four bars (representing one digit) will have a black-white-black-white pattern. Stop when you have six additional groups of four digits each, and do not decode the extra-long bars on the right. Now that you have figured out which bars (of different widths) correspond to each number, all you need is to know the code that translates these into the actual digits in the 12-digit number. Use the following instructions to do so:   3211 = 0  2221 = 1  2122 = 2  1411 = 3  1132 = 4  1231 = 5  1114 = 6  1312 = 7  1213 = 8  3112 = 9 If the numbers are printed beneath the bar code, read them to see whether you made any mistakes. You can also look up the product in the GTIN database, typing in the 12-digit barcode you found into the "GTIN" field. This should find any product from a company that was officially assigned a barcode, although sometimes companies mistakenly print their own barcodes that aren't added to the system. Still, most of the time, this database should come up with a product name that matches the item you are looking at, if you read the barcode correctly.
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