Advanced options
Throw ratio = distance / image width, printed in the projector's spec (often as a zoom range like 1.2-1.5:1). Screen sizes quote the diagonal. Viewing-distance guide: sit about 1.2-1.6x the screen diagonal away for cinema-like immersion.
What The Projector Distance Calculator Works Out
- Image size: the throw ratio is distance divided by image width, so width is distance divided by throw ratio, and the 16:9 height and diagonal follow by Pythagoras. A standard 1.2:1 projector 3 m from the wall paints an image 2.5 m wide, about a 113 inch diagonal.
- Distance for common screens: the same ratio read backwards for 80, 100 and 120 inch screens; a 100 inch screen needs a 1.2:1 projector about 2.66 m back. Zoom lenses quote a range (1.2 to 1.5:1 is the domestic norm) giving placement slack; short throws around 0.5 fill a wall from a coffee table and ultra-short-throw laser units at 0.25 or less sit on the TV cabinet itself.
- Custom throw ratio (advanced): enter the exact figure from the spec sheet (1.37, 1.65 and so on) instead of the five presets, with an optional long-end figure for the zoom range.
- Zoom range (advanced): when a long-end throw ratio is given, the calculator shows the image size at both ends from your distance and the full mounting range for a chosen screen, so you know whether the bracket position has to be exact.
- Image aspect ratio (advanced): 16:10 for business projectors, 4:3 for older models or 2.35:1 for a cinemascope screen. 16:9 arithmetic converts any diagonal to width by multiplying by 0.872; the other shapes use their own factor.
- Distance for the screen you want (advanced): the reverse shopping sum: the mounting distance (or range, with zoom) for a screen of so many inches, and how far your current position is from it. Lens shift moves the image without keystone distortion; digital correction fakes that at the cost of sharpness, so avoid keystone wherever geometry allows.
- Image brightness (advanced): lumens times screen gain divided by the image area in square feet gives foot-lamberts (shown with nits too). SMPTE aims for 14 to 16 fL in a dark room; a dimly lit living room wants 20 to 40. Area grows with the square of the diagonal, so a 120 inch picture spreads the same lumens over more than double an 80 inch one, which is why ambient light demands either lumens, smaller images or blackout.
- Screen gain (advanced): 1.0 is a matte white screen; grey ALR (ambient light rejecting) screens run 0.6 to 0.9 and high-gain screens 1.3 or more at the cost of viewing angle. Screens beat painted walls on uniformity and gain.
- Recommended seating (advanced): 1.2 to 1.6 times the diagonal, the THX-style zone for cinema immersion. A 3 m sofa distance comfortably supports a 100 inch plus image, the scale at which projection undercuts equivalent TVs on price.
- Screen sizes table (advanced): width and height, mounting distance (with zoom range), brightness if lumens are given and the seating zone for seven screen sizes from 80 to 150 inches.