Projector Throw Distance & Screen Size Calculator
Work out throw distance, screen size and required throw ratio for any projector or lens — any brand works. Enter your lens throw ratio and screen size, then use your projector lumens to check image brightness.
Throw ratio (distance ÷ image width)
Image brightness
Image brightness
Recommended viewing distance
Recommended DHN models
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How this calculator works
A projector's throw ratio tells you how far it must sit from the screen to fill a given image width. All calculations below use the standard industry formulas — the same ones used by professional AV integrators when planning an installation.
Throw distance
Throw distance = throw ratio × image width. For example, a 1.5:1 lens filling a 3 m wide screen must sit 4.5 m away. If you use a zoom lens, enter its wide-end value for the nearest valid position, and its tele-end value for the farthest.
Image brightness
Screen brightness (foot-lamberts) = lumens × screen gain ÷ screen area in square feet. Divide again by 10.76 for candela per square metre (cd/m²). Larger screens spread the same light over more area, so brightness falls as the image grows.
Reference brightness targets
- Dark home cinema: 16 fL (SMPTE reference), 14–30 fL typical.
- Low ambient light / meeting rooms: 30 fL or more.
- Bright rooms, exhibition halls and daylight venues: 50–70 fL or more — or choose a higher-lumen model.