How to calculate what a screen’s specs don’t tell you

Dave Farquhar Hardware

Last Updated on November 30, 2018 by Dave Farquhar

If you want to quickly and easily calculate the pixels per inch of a display, here’s a useful tool:

http://members.ping.de/~sven/dpi.html

You can use a calculator to calculate pixels per inch, dot pitch, and other cool stuff from just the resolution and diagonal size.

While this tool calculates the pixels per inch for you, it also calculates the width and height of a screen. And dot pitch! Remember dot pitch? If you have a bunch of scanned documents and intend to use a tablet or e-reader to view them, this will help you determine the size of display that best matches the size of your originals. I can read a scanned magazine page on a 7-inch tablet, but I wouldn’t call it comfortable. Even a 10-inch tablet falls short, but if you rotate it to landscape mode you can view about half a page at a time and read it comfortably.

Among the things I found: A 27-inch WQHD 2560×1440 display delivers 108.79 pixels per inch. A relatively cheap 21.5-inch 1920×1080 display delivers 102.46 pixels per inch. So if you’re just after a sharp display, a pedestrian 21.5-inch 1080p display, commonly available for less than $150, is surprisingly good for that.

If you’re in the market for a tablet or a monitor, this tool is worth bookmarking.

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