Pixel ruler - Measure the Length in Pixels
A ruler with pixel indication, to measure pixel length in graphics. The smallest intervals on the ruler have a width of 5 pixels, intervals of 10, 50, 100, 500 and 1000 pixels have elongated dashes. The ruler has a length of 2000 pixels. You can use the ruler graphics freely at will.
An indication of inches or centimeters is not possible without knowing the exact dimensions of your screen. So you would have to get a ruler to measure your screen. Then, you have a ruler anyway, without measurement errors.