# How do you calculate DPI for a mobile phone?

If you know the resolution and screen size, how do you calculate DPI on a mobile phone screen? I hate maths :-P

matt101101 / MOD Jan. 8, 2012 at 20:37

I think you mean PPI? As for the maths, Google it. I bet it'll take less than 30 seconds to find the equation you want.

matt101101 / MOD Jan. 8, 2012 at 20:39

I did it for you:

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:

blizzard7 Jan. 8, 2012 at 21:30

Or you can be lazy like I am:

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

CTPAHHIK Jan. 9, 2012 at 12:08

I prefer to be lazy.

matt101101 / MOD Jan. 9, 2012 at 12:43

As do I...

The maths is just copied and pasted from Wikipedia .

Most Useful Answer matt101101 Jan. 8, 2012 at 20:39

I did it for you:

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: