PDA

View Full Version : Calculating Monitor Height and Width from Diagonal Size


Oj0
03-11-2010, 03:08 AM
Alright, so you want to buy a new 30" monitor but you'd like to know the exact height and width of the panel. How do you do it? Simple. You need the following:


Horizontal size (hypotenuse) of screen
Aspect ratio


For my example, I'm going to use a 19" 16:9 aspect ratio screen.

We are going to be using the formulae

sin(tan-1 height/width aspect ratio)*diagonal for height, and
cos(tan-1 height/width aspect ration)*diagonal for width



Fistly, 9/16 to get a decimal aspect ratio: 0.5625
Using tan-1, we can work out the diagonal angle of the screen. tan-1 0.5625 = 29.358 , meaning the angle is 29.358° from horizontal.
Use the following formula: sin (tan-1 result) * (diagonal size, hypotenuse) : sin 29.358 * 19: sin 29.358 = (0.49067565355234651434427338183771) * 19 = 9.3228374174945837725411942549166 = 9.32" high
Use the following formula: cos (tan-1 result) * (diagonal size, hypotenuse) : cos 29.358 * 19: cos 29.358 = 0.87157342826278517733892936862199 * 19 = 16.559895136992918369439658003818 = 16.56" wide


So we can see that the HxW of a 19" 16:9 widescreen monitor is 9.32" x 16.56"

How often do you see people referring to 2 x 19" monitors side by side as an effective 38"? This is incorrect, to get 38" diagonal you have to QUADRUPLE the area - i.e. double the 9.32" height to 18.64" as well as the width from 16.56" to 33.12". To calculate the actual diagonal of two monitors (using the specifications from the above example), we use the following formula, otherwise known as Pythagoras' Theorem:


a² + b² = c² , where c is the hypotenuse


For two 19" monitors side by side, we retain a height of 9.32" and double our width to 33.12"
To work out our new hypotenuse, or diagonal size, we can do the following:


((9.32²)+(33.12²))sqrt, or
((9.32² = 86.8624) + (33.12² = 1096.9344) = 1183.7968) sqrt = 34.406348251449179331286630792993 = 34.41" = 34.5"


I hope that clears things up for anyone interested :)

knopflerbruce
03-12-2010, 02:58 PM
You need a lesson on rounding of numbers, but apart from that, very good! B+!

:D

Oj0
03-12-2010, 03:50 PM
For the last part I rounded to the nearest half inch as monitors are never advertised as 21.4" or whatever ;)

john123
04-05-2010, 04:16 AM
nice it needs to be rounded up but never the less its job well done