Barcode Size and DPI Calculator
A barcode only scans when its thinnest bar (the module or X-dimension) is printed at the right width. This calculator turns a module size and a barcode type into the full width and height, and then into printer dots, because a printer cannot draw half a dot: at 203 dpi a 0.33 mm module is 2.64 dots, so it prints as 3 dots (0.375 mm).
For retail codes the standard size is 0.33 mm per module (100%) and the allowed range is 80% to 200%. Make the barcode with the Print Label / PDF page, which can set the exact size in mm, cm, inch or pixels, and print on label sheets.
Rules of thumb
- Leave an empty quiet zone on both sides: 11 modules left and 7 right for EAN-13, 9 each for UPC-A, 10 for Code 39 and Code 128.
- Choose a module that is a whole number of dots at your printer's resolution. Thermal printers at 203 dpi print cleanly at 3 or 4 dots (0.375 or 0.5 mm).
- Code 128 and Code 39 bars should be at least 6.35 mm (0.25 in) tall, or 15% of the bar width, whichever is larger.
- Always test a printed sample with the scanner that will be used. Print contrast and paper matter as much as size: see the color contrast checker.