Projector Throw Distance Calculator — Universal & Free
Free online calculator that finds the right projector placement using raw throw ratio. Three modes: forward (ratio + screen size → distance), reverse (distance + ratio → maximum screen size), and find-ratio (distance + screen size → required throw ratio so you know which class of projector to buy). Built-in throw-ratio classes for ultra-short, short, standard and long-throw projectors. Top-down setup diagram, metric and imperial units, shareable URL.
How to calculate your projector distance
Look on your projector spec sheet for "throw ratio" — usually a range like "1.20 – 1.60". If you have only the model name, search "[model] throw ratio".
Pick aspect (16:9 for most home projectors), enter the screen diagonal — inches if you bought a fixed screen, centimetres if you are wall-projecting.
The result shows the lens-to-screen distance, image width and height. Confirm your room is long enough and there are no obstacles in the light cone.
If you only know how much room you have, switch to reverse mode and enter the distance — the calculator returns the largest screen that fits.
Universal calculator — works with any throw ratio, no model lookup needed
Setup diagram
Features
FAQ
What is throw ratio?
Throw ratio is the distance from the lens to the screen divided by the image width. A throw ratio of 1.5 means the projector needs to be 1.5 metres away to produce a 1-metre-wide image. Lower throw ratios mean the projector can be closer to the screen.
How do I find the throw ratio of my projector?
Open the projector spec sheet (PDF or website) and search for "throw ratio" — it is usually a range because most projectors have a zoom lens. Use the middle of the range for a starting estimate, then fine-tune by zooming.
Can I use this for ultra-short-throw (UST) projectors?
Yes. UST projectors typically have throw ratios from 0.20 to 0.45 — pick "Ultra-short throw" preset or enter the ratio directly. Note that UST throw ratio is measured along the floor, not horizontally to the lens, so verify with your projector's placement diagram.
Why is throw ratio a range and not a single number?
Most projectors have a zoom lens, so they can produce the same image size from a range of distances. The two ends of the range are the closest (smallest throw ratio, largest image) and farthest (largest throw ratio, smallest image) you can place the projector.
Does this account for vertical lens shift or keystone?
No — the calculator returns the lens-to-screen straight-line distance. If you use vertical lens shift, the projector itself may be higher or lower than the screen centre, but the throw distance does not change. Avoid keystone correction if you can — it reduces sharpness.
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