SiliSoftware is free to use.
But if you want to donate, please do :)
Source code available upon request (donation appreciated)
SiliSoftware » Tools » Screen Aspect Ratio & Dimension Calculator

Screen Aspect Ratio & Dimension Calculator

Calculate image dimension (in pixels) from total number of pixels and aspect ratio

Aspect Ratio: square 5:4 4:3 3:2 16:10 16:9 1.85 2.35
Pixels:

Calculate the missing value from two of height, width and/or aspect ratio

Aspect Ratio: square 5:4 4:3 3:2 16:10 16:9 1.85 2.35
Width: Height:

Calculate optimal viewing distance from screen size

For a screen that is ( in | cm ) diagonal and ( 4:3 | 16:9 ), the optimal viewing distance is between and , ideally around (based on screen height (4H-8H,6H))
alternately: between and , ideally around (based on screen width (2W-5W,3W))

Calculate screen dimensions (height/width/area, in inches or cm) from diagonal measurement and aspect ratio

Diagonal
Width
Height
Aspect Ratio
Area fullscreen
4:3 movie
3:2 photo
16:9 movie
2.35 movie

  Actual Area Relative Area
Diagonal Ratio Width Height Full 4:3 3:2 16:9 2.35 Full 4:3 3:2 16:9 2.35