Calculation of Monitor PPI
Theoretically, PPI can be calculated from knowing the diagonal size of the screen in inches and the resolution in pixels (width and height). This can be done in two steps:
1. Calculate diagonal resolution in pixels using the Pythagorean theorem:
2. Calculate PPI:
- is diagonal resolution in pixels
- is width resolution in pixels
- is height resolution in pixels
- is diagonal size in inches (this is the number advertised as the size of the display).
For example, for a 21.5 inch (54.61 cm) screen with a 1920×1080 resolution (in which = 1920, = 1080 and = 21.5), we get 102.46 PPI; for a typical 10.1 inch netbook screen with a 1024×600 resolution (in which = 1024, = 600 and = 10.1), we get 117.5 PPI.
Note that these calculations may not be very precise. Frequently, screens advertised as “X inch screen” can have their real physical dimensions of viewable area differ, for example:
- Apple Inc.'s Mid-2011 iMac is advertised as a "21.5 inch (viewable) display," but its actual viewable area is 545.22 mm or 21.465 inches. The more precise figure increases the calculated PPI from 102.46 (using 21.5) to 102.63.
- The HP LP2065 20 inch (50.8 cm) monitor has an actual viewable area of 20.1 inch (51 cm).
Famous quotes containing the words calculation of, calculation and/or monitor:
“To my thinking boomed the Professor, begging the question as usual, the greatest triumph of the human mind was the calculation of Neptune from the observed vagaries of the orbit of Uranus.
And yours, said the P.B.”
—Samuel Beckett (19061989)
“Common sense is the measure of the possible; it is composed of experience and prevision; it is calculation appled to life.”
—Henri-Frédéric Amiel (18211881)
“It is indeed typical that you Earth people refuse to believe in the superiority of any world but your own. Children looking into a magnifying glass, imagining the image you see is the image of your true size.”
—Franklin Coen. Joseph Newman. The Monitor (Douglas Spencer)