Here's how to manually calculate the pixel density of your smartphone's display
posted by Peter K. / Nov 12, 2015, 8:40 AM
Color reproduction and overall properties aside, the pixel density is one of the more vital aspects of a display, regardless of the gadget it is "attached" to. It's an area in which our smartphones have witnessed a staggering growth in the past few years and it seems that the resolution bumps won't stop anytime soon. Let's talk about pixel density a bit, shall we?
Now, in case you're a smartphone geek, you certainly know what's the pixel density of your phone's screen. In case you don't (which we highly doubt, but still), there's an easy way to get around and calculate it on your own. Actually, there are two ways to do so, and have in mind that we're not taking a regular Google search as a viable option, since it's trivial and mainstream!
The more mundane and harder way is the old school manual one, which requires you to do some math. How long has it been since you've last exercised your algebra, hmm? Let's do it now. You need to know the resolution of the display as well as its diagonal. Provided that you have both in hand, you can apply them in the following formula, which is a slightly modified variation of the Pythagorean theorem:
With the above equation in mind, let's manually calculate the pixel density of a 5.3-inch 1080p display. As its resolution is 1080 by 1920 pixels and its diagonal 5.3 inches, we input these into the formula:
We square the width and the height of the display, then we add them to one another, and finally, find the square root of the sum in question. The outcome is the diagonal resolution of the display.
Finally, we divide by the screen diagonal and we get the sought pixel density number.
So, this is how the pixel density of a given display is usually found. That's the formula which is used in most cases. Of course, it's rather cumbersome and we doubt that anyone would actually use this in a real-life scenario. Still, it's curious to see what lies beneath the numerous PPI calculators available on the interwebs. Yes, these are extremely useful and we are used by just everyone. One of our favorite ones is made by Sven Neuhaus and can be found at https://www.sven.de/dpi/. It's as straightforward as it gets: you input the resolution, the display diagonal, and voila, the tool calculates the pixel density straight away. Here is it in action:
Of course, it's not the only PPI calculator available out there. What's your favorite one?
Posts: 258; Member since: Feb 22, 2014
like I'm going to remember that.
posted on Nov 12, 2015, 8:43 AM 1
Posts: 661; Member since: Jun 05, 2012
That's why they made this article. So you can refer back to it if you need it. Or you can write the formula down. Or you can look up the phone in question on PhoneArena and it will tell you what it is. But really, if you're that bad at maths that you can't figure this out then maybe you shouldn't be concerning your little head with such big ideas as screen pixel density...
posted on Nov 12, 2015, 8:59 AM 1
Posts: 17093; Member since: Jun 17, 2009
It's just the Pythagorean theorem. The sum of the square of each side of a right triangle equals the square of the hypotenuse. So just take the sum of the two squares. Then take its square root. That gives you the number of pixels diagonally. Divide that by the number of inches diagonally, and you have pixels per inch. It's easy because the resolution of any display is advertised, and so is it's diagonal measurement in inches. You can also use it to calculate the two sides of the display in inches.
posted on Nov 12, 2015, 8:56 AM 3
Posts: 2318; Member since: Aug 14, 2014
I took my Nexus 4 and got 300.24. That's with the on screen buttons. With the full screen I get 317.8 PPI. Pretty handy I must say!
posted on Nov 12, 2015, 9:30 AM 2
I've been using this http://thirdculture.com/joel/s
posted on Nov 12, 2015, 10:33 AM 0
Posts: 4744; Member since: Jan 28, 2011
I've been doing these calculations for years, because I am a giant nerd. Come to think of it, this may be the only application for the Pythagorean Theorem I've encountered since high school.
posted on Nov 12, 2015, 10:11 PM 0
Posts: 14; Member since: Aug 28, 2015
The one that I wrote myself 6 years ago. It also gives me the size of the diaplay in mm and the area of it in cm2.
posted on Nov 13, 2015, 12:17 AM 0
Posts: 314; Member since: Nov 13, 2013
posted on Nov 13, 2015, 5:51 AM 0
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