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How big will it be? Projector throw distance calculator

Tell us where the projector will sit and how much wall you have. You'll see the picture each projector from our guide makes from that spot, whether it fits, how far back it needs to be for the size you want, and whether it's bright enough for your room.

1 Where will the projector go?
2 Your measurements
Units

Ultra-short-throw units sit on a low console a few inches from the wall.

Aspect ratio: 16:9, the native shape of every projector here.

3 How bright is the room when you watch?
How it works and assumptions (tap to edit)
  • Image shape: for a 16:9 picture, width = diagonal × 0.872 and height = diagonal × 0.490.
  • Throw ratio: distance ÷ image width. So image width = distance ÷ throw ratio, and distance = throw ratio × width. A zoom lens has a range (wide end makes the biggest picture); a fixed lens has one number.
  • Makers' charts first: where the manufacturer publishes a distance chart, we interpolate between its rows instead of using the ratio. Epson measures from the lens; Hisense measures its ultra-short-throw from the back of the console to the wall, and allows about 5% deviation.
  • Distance: for normal projectors, measure from where the front of the lens will be. Behind the couch, on a shelf and on the ceiling use the same math; placement only changes which projectors make sense.
  • Brightness: rated lumens are what the maker quotes in its brightest mode, and brands use different standards (ANSI or ISO 21118), so treat small gaps as a tie. Real pictures get dimmer in calmer modes and as lamps age. The defaults are reviewer guidance for a 100-120 in picture, citing Projector Central: about 1,500 for a dark room, 2,500+ with some light, 3,000+ for daytime (source). "Just under" means within 15%.
  • Screens matter: in daylight a light-rejecting screen helps more than a few hundred extra lumens, ultra-short-throw projectors need a UST-specific one, and nothing beats direct sun on the screen (AV.com).

Projector figures this calculator uses (3, from our guide)
ProjectorThrowBrightnessSource
Hisense PX3-PRO TriChroma Laser UST ProjectorUltra-short-throw: 4.7-18.1 in from the wall for 80-150 in3,000 lumens (ANSI)Hisense PX3-PRO spec sheet throw distance chart (back of console to wall); 3,000 ANSI lumens
Optoma UHD38x1.5-1.66:1, 1.1x zoom, 33-300 in4,000 lumens (ANSI)Optoma UHD38x spec page and spec sheet: 1.5-1.66:1 throw, 1.1x zoom, 33-300 in, 4,000 ANSI lumens
Epson Home Cinema 23501.33-2.15:1, 1.62x zoom, 40-500 in2,800 lumens (ISO 21118)Epson Home Cinema 2350 User's Guide projection distance table (lens to screen); 2,800 lumens white (ISO 21118)

Distances are the makers' figures and can vary a few percent between units; confirm with the projector in place before drilling for a ceiling mount. Keystone correction can shrink or square a picture but costs sharpness, so this calculator doesn't count on it.

The math, in two lines

A 16:9 picture is 0.872 times its diagonal wide, so a 100 in screen is about 87 in (7.3 ft) wide. A projector's throw ratio is distance divided by that width. The Optoma UHD38x's 1.5 to 1.66 ratio means 1.5 × 87 = 131 in to 1.66 × 87 = 145 in from lens to screen, roughly 10.9 to 12.1 ft. Where a maker publishes its own distance chart, as Epson and Hisense do, the calculator reads between the chart's rows instead.

Ultra-short-throw is a different measurement

An ultra-short-throw projector sits under the picture, so the number that matters is the gap between the back of the unit and the wall. Hisense's chart for the PX3-PRO puts a 100 in picture at 8.5 in from the wall and a 150 in picture at 18.1 in, with the bottom of a 100 to 150 in picture about 15 to 22 in above the surface the console stands on. That is why the calculator switches to inches when you pick "Right against the wall".

Size and brightness pull against each other

The same lumens spread over a bigger picture look dimmer: a 130 in image has about 40% more area than a 110 in one. In a room you can't darken, a slightly smaller picture on a light-rejecting screen usually looks better than the biggest one your wall allows.

Guides that use this calculator