Projector Lumens Calculator

This calculator estimates the projector brightness, in lumens, needed to hold a target contrast against the ambient light landing on the screen. It scales with the screen area and the contrast ratio you pick for the content: 7:1 passive viewing, 15:1 basic decision-making such as presentations, 50:1 analytical work such as artwork or medical imaging, or 80:1 full-motion video such as home theater, assuming a unity-gain screen with a standard derating factor. Enter the ambient light at the screen in foot-candles (imperial) or lux (metric), the screen width and height, and the contrast target. Brighter rooms and higher contrast push the required output up quickly.