How far should a projector be from a 100-inch screen?

It depends on the throw ratio: a 1.0 ratio sits about 7.3 ft back, 1.5 about 11 ft, and an ultra-short-throw under 2 ft.

Do I measure from the lens or the back of the projector?

From the lens. Add the projector's body length (about a foot) plus cable space when planning the shelf or mount.

How do I convert a screen diagonal to width?

For 16:9, multiply the diagonal by 0.872 for width and 0.490 for height. A 120-inch screen is 105 inches wide.

Guide

How to calculate projector throw distance

Throw distance = image width × throw ratio. Here is the step-by-step formula, the 16:9 diagonal-to-width conversion, and a ready table by throw ratio.

Guide

Throw distance = image width × throw ratio. First convert the screen diagonal to width (for 16:9, width = diagonal × 0.872), then multiply by the projector's throw ratio. For a 100-inch screen (87 inches wide) and a 1.5 throw ratio: 87 × 1.5 = 131 inches, about 11 feet.

Two steps: get the image width from the diagonal, then apply the throw ratio. For a 16:9 screen, width = diagonal × 0.872 and height = diagonal × 0.490. Measure from the lens, and leave roughly a foot for the projector body and cables behind it.

Throw distance by throw ratio (for 100- and 120-inch screens)

Throw ratio	100″ screen	120″ screen
0.25	1.8 ft	2.2 ft
0.50	3.6 ft	4.4 ft
0.80	5.8 ft	7.0 ft
1.00	7.3 ft	8.7 ft
1.20	8.7 ft	10.5 ft
1.50	10.9 ft	13.1 ft
2.00	14.5 ft	17.4 ft

Frequently asked questions

Distance = image width × throw ratio. Convert the diagonal to width first (16:9: width = diagonal × 0.872).

Calculator →Throw distance by screen size →Projectors →