Projector Throw Distance Calculator
A 100 inch 16:9 screen is 87.2 inches wide, so a projector with a 1.5 throw ratio sits 10.9 ft (3.32 m) away. A 1.37 to 1.64 zoom lens gives 10.0 to 11.9 ft. From 10 ft, the same projector throws a 92 inch image.
How to use
- Pick Find distance to learn where to put the projector for a screen size, or Find screen size to see what image you get from a given spot.
- Choose US units (inches, feet) or metric (centimeters, meters) and the screen shape: 16:9, 16:10, 4:3 or 2.35:1.
- Enter the screen as a diagonal or a width, or enter the distance from the lens to the screen.
- Enter the throw ratio from the projector spec sheet. For a zoom lens enter the shortest (wide) and longest (tele) ratio, such as 1.37 and 1.64.
- Read the distance range, the screen width, height and diagonal, and check the side-view diagram.
How it works
Throw ratio = throw distance / image width, measured from the lens to the screen. So distance = throw ratio x width, and width = distance / throw ratio. A ratio of 1.5 means the projector sits 1.5 feet back for every foot of image width.
Screen width and height come from the diagonal and the aspect ratio a = width / height: width = diagonal x a / sqrt(a^2 + 1) and height = width / a. A 100 inch 16:9 screen is 87.2 inches wide and 49.0 inches tall. The aspect ratios used are 16:9 (1.778), 16:10 (1.6), 4:3 (1.333) and 2.35:1 (2.35).
A zoom lens lists a range, for example 1.37 to 1.64. The shortest ratio gives the closest placement and the longest ratio the farthest, so the projector can sit anywhere between those two distances for the same image. In Find screen size, the shortest ratio gives the largest image.
These are nominal values. Check the manual, since some brands measure the ratio for the full image width at the widest zoom, and lens shift, keystone correction and a tilted projector change the usable position a little. Allow a few inches of margin, and measure the actual distance from the lens, not the back of the projector.
Common throw types
| Type | Throw ratio | Distance for 100 in 16:9 |
|---|---|---|
| Ultra short throw | under 0.4 | under 2.9 ft (0.9 m) |
| Short throw | 0.4 to 1.0 | 2.9 to 7.3 ft (0.9 to 2.2 m) |
| Standard throw | 1.0 to 2.0 | 7.3 to 14.5 ft (2.2 to 4.4 m) |
| Long throw | over 2.0 | over 14.5 ft (4.4 m) |
FAQ
What is a throw ratio?
It is the projection distance divided by the image width. A 1.5:1 projector throws a 100 inch wide image from 150 inches away. Lower ratios mean a shorter throw, so the projector can sit closer.
How far should a projector be from a 100 inch screen?
For a 16:9 screen the width is 87.2 inches. A typical 1.5 throw ratio puts the projector about 10.9 ft (3.3 m) away. Short throw models under 1.0 need less than 7.3 ft (2.2 m).
How do I read a throw ratio range like 1.37 to 1.64?
That is the zoom range. At full wide zoom the ratio is 1.37 and the image is biggest for a given distance. At full tele it is 1.64. Enter both values to get the nearest and farthest placement.
Does the aspect ratio change the distance?
For the same diagonal, yes. A wider shape is a wider image, so a 2.35:1 screen needs a longer throw than a 4:3 screen of the same diagonal. For the same width, the distance stays the same.
What about ultra short throw projectors?
They have ratios around 0.2 to 0.4 and are measured the same way. Enter 0.25 and the result is the distance from the lens to the screen, which may be only a foot or two.