Converting real world units to computer pixels?

[Ch1156]

Is it even possible? i want to be able to convert like feet to pixels or something but how would i do that?

I found this

http://www.worldatlas.com/aatlas/infopage/pixels.htm

Would that be right?

[sfBlackfox]

It's actually a quite simple equation but there is no constant value like the site mentions.

Consider the following:
Your computer screen is a full hd: 1920x1080

This is in fact an equation.

Now consider you have a 22' monitor.

(1920x1080)/22 = size of 1 pixels/inch;

[Ch1156]

But not everyone has the same screen size, will that effect the value?

[sfBlackfox]

Yes, and not everyone has the same resolution either.
A pixel has a relative size, and is not constant.

Think of it this way, The latest IPAD has a screen retina display with 2048 x 1536 resolution and according to their website has 3,1 million pixels.

The density of pixel and size far outweigh my older 22' monitor with a resolution of 1680x1050. Yet that screen is so much bigger!

Or another angle, a camera can capture 12MP. But all those pixels fit on the size of 3.5 inch sensor.

[helios]

Simply put, there's no way to do it without doing some calibration. The computer can't possibly know the dimensions of the screen you've plugged in.

The easiest method involves taking a ruler or any other measuring implement, putting it against the screen, and inputting both the width and height into the program. There are ways of determining the desktop resolution, so after that it's just a matter of dividing a couple times.