Pixels per mm on screen

Posted on 2012-09-20
Medium Priority
Last Modified: 2016-04-20
Hello All,

I have been able to get the screen resolution. Now I want to calculate pixels per mm on that screen resolution. Any ideas on what will be the formula for that?

Thanks for any help.

Parag T
Question by:starkinfotech
LVL 14

Expert Comment

ID: 38416803
here is a calculator for DPI
just get the answer (PPI - Pixels Per Inch) from that and divide by 25.4 to get ppmm
LVL 44

Accepted Solution

Darr247 earned 1336 total points
ID: 38416851
Take the resolution size and divide it by the screen size in mm.

Resolution    Size
1680    /     334mm = 5.0299 pixels/mm  horizontal
x             x
1050    /     206mm = 5.097 pixels/mm  vertical

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LVL 84

Assisted Solution

by:Dave Baldwin
Dave Baldwin earned 664 total points
ID: 38416911
You know that different size monitors that are displaying the same pixel resolution will have different pixels per mm.  My 19 inch and 17 inch monitors are both set to 1280x1024 pixels.  But because the physical sizes are different, the pixels per mm will be different.
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LVL 44

Expert Comment

ID: 38417073
Precisely so, DaveBaldwin...
And I should have said divide native resolution by the screen size. Usually, on LCDs, if you force it lower than its native resolution, it will merely make the black border around the edges wider... and the pixels per mm would stay the same.

Author Comment

ID: 38417250
So screen size(Diagonal) is also a important factor in calculating pixel per mm.

Is there any way to get the screen size(Diagonal) by using c#?

Parag T
LVL 44

Assisted Solution

Darr247 earned 1336 total points
ID: 38417302

The diagonal size is the square root of (ScreenWidth squared + ScreenHeight squared).
LVL 14

Expert Comment

ID: 38417543
are you entering the dimensions manually? the diagonal dimension isn't important, the example website uses the diagonal dimension and then calculates the  length and width of the screen, and then uses that in the calculation Darr247 provides.

the calculation on that webpage is done in javascript.

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