How to Use the Projector Viewing Distance Calculator
The calculator needs three pieces of information:

1) How far you sit from the screen, measured in feet.

2) What shape is your screen?

3) What is the size of the screen? You may enter either the diagonal screen size or the screen width. (If you enter screen width, don’t forget to check the appropriate radio button)

If you do not specify a viewing distance, the calculator will tell you what the optimal seating distances are for the selected screen size.