Calculate projector lumens
This calculator can tell you how much lumens your projector needs
Ambient light at screen: this is how much light there is on the screen.
Desired contrast ratio:
7 for Passive viewing
15 for Basic decision making
50 for Analytical decisioin making
80 for Full motion video or home theater
Screen area: the area of the screen, in square meter or feet.
Screen gain this is normally 1.
Projector deration this is normally 0.75