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Projector Throw Calculator

Throw ratio is the one number that decides where a projector goes: distance divided by image width. A ratio of 0.5 fills a wall from almost against it; 2.0 needs a long room. The consequence people miss is brightness — doubling the image width quadruples its area, and the same lumens spread across four times as much surface look markedly dimmer.

What this generator does

Divides the throw distance by the throw ratio to get the image width, derives the 16:9 height, and reports the equivalent beam angle and the area the light has to cover.

How to use this tool

  1. Enter the throw distance and the projector's throw ratio.
  2. Read the image width and the 16:9 height that goes with it.
  3. Note the area — that is what governs how bright the image looks.
  4. Try a lower ratio to see how much closer a short-throw lens sits.

Understanding the controls

Throw distance
How far the projector is from the screen, in metres.
Throw ratio
Distance divided by image width, from the projector's specification. Lower is wider: 0.5 is short-throw, 1.5 is typical, 2.0 needs a long room.

Common use cases

  • Working out where to mount a projector for a given screen
  • Checking whether a room is long enough for a projector you own
  • Choosing between a standard and a short-throw lens
  • Understanding why a bigger image always looks dimmer
  • Planning a projection setup before hiring equipment

How this generator works

This is the same trigonometry as a lighting beam, expressed the way projector manufacturers quote it. The check confirms the width and the equivalent angle recover each other in both directions, that the throw ratio really is distance over width, and that the image comes out at 16:9.

Randomness and fairness

Nothing here is random. The image size follows entirely from the distance and throw ratio you enter.

For how randomness is produced across the whole site, see how Generate Random works.

Limitations and good to know

  • A 16:9 image is assumed. Other aspect ratios change the height but not the width for a given throw.
  • Lens shift and keystone correction both change the geometry and neither is modelled.
  • Brightness is reported as area only — actual perceived brightness depends on lumens, screen gain and ambient light.
  • Zoom lenses have a range of throw ratios rather than one; use whichever end you intend to work at.

Privacy and your data

Every figure is computed in your browser and nothing you enter leaves the device.

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