PPI Calculator

This tool turns a pixel resolution and a screen diagonal into a pixel density. Enter the horizontal and vertical pixel counts with the diagonal in inches and it returns the PPI, the dot pitch in millimetres, the physical width and height, the aspect ratio and the distance at which 20/20 vision stops separating one pixel from the next. Two other actions run the sum backwards, giving the screen size a resolution implies at a chosen density, and the density a chosen viewing distance actually calls for. Screens are sold by an advertised diagonal that is often a fraction smaller than the measured picture, so measure the glass if you want the density to be exact.

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Sizes In
The diagonal is read in this unit, and the width, height, area and resolving distance come back in it. The density is pixels per inch either way, because that is what PPI means.
The diagonal a screen is sold by, measured corner to corner across the visible picture. Panels are advertised by an inch figure worldwide, and EU listings usually print the centimetre figure beside it -- a "139 cm (55 in)" television is either number, whichever you have to hand.
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Show Sizes In
Which unit leads on the diagonal, width, height and resolving distance below. The other is printed beside it either way.
Pixels per inch, which is how every panel datasheet quotes density. Divide a pixels-per-centimetre figure by 0.3937 if that is what you have.
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Distances In
How far you sit is measured with a tape, not read off a spec sheet, so pick whichever tape you own.
Pixels per inch, as every datasheet quotes it.
About 12 in for a phone, 24 in for a desk monitor, 100 in for a living room television -- 30 cm, 60 cm and 2.5 m. A blank box uses 24 in, or 60 cm.
An arcminute is an angle, so it is the same standard in every market.
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