Projector Lumens and Throw Ratio, Explained

The short answer

Two numbers decide whether a projector fits your room:

• Lumens: how much light it puts out. More lumens keep the picture visible when room lights or daylight are on, and they help fill a larger screen.
• Throw ratio: the distance from the lens to the screen divided by the width of the image. A lower ratio means the projector can sit closer for the same picture.

Of the 318 projectors listed on Wiki Shopping on October 26, 2026, 129 state a brightness that fits our ranges, and 44 are sold as short throw or ultra short throw.

What lumens measure

A lumen is a unit of light output. For projectors, the standard figure is the ANSI lumen: the projector shows a full white image, light is measured at nine points across the screen, and the average is multiplied by the screen area. Wikipedia notes that this method is generally more accurate than other ways the industry measures brightness, so prefer listings that say ANSI lumens.

Two things change how bright the picture looks:

• Room light. Lamps and daylight wash out a projected picture, so a lit room needs more lumens than a dark one.
• Screen size. The same light spread over a bigger image looks dimmer. A 120 inch image has 1.44 times the area of a 100 inch image, so each part of it gets about 30% less light.

How throw ratio works

Throw ratio is distance divided by width, both in the same unit. BenQ's example: at a ratio of 2.0, the projector sits 2 feet back for every foot of image width, so 10 feet gives a 5 foot wide picture.

Use the image width, not the diagonal. A 100 inch 16:9 image is about 87 inches wide. At a ratio of 1.5, the lens must sit about 131 inches (about 10.9 feet) from the screen. A zoom lens lists a range of ratios, which gives you a range of positions.

BenQ's own models show the difference a short throw lens makes: for a 100 inch image, its TK710 sits 8.4 feet away and the short throw TK710STi sits 6.5 feet away.

Which throw type fits your room

Resolution and light source

On Wiki Shopping, 1080p leads with 92 projectors, ahead of 4K with 86. For the light source, 57 use a laser and 10 list LED.

How we count

Counts are Wiki Shopping filter pages for projectors, read from our database on October 26, 2026. A projector counts when its store listing states brightness, throw type, resolution or light source; listings that do not state them are left out of those counts. The 87 inch width, 131 inch distance and 1.44 area figures are our arithmetic: a 16:9 image is 16 divided by the square root of 337 (about 0.87) times its diagonal wide, and area grows with the square of the diagonal.

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Sources

1. en.wikipedia.org: Lumen (unit)
2. en.wikipedia.org: Throw (projector)
3. benq.com: what is throw ratio for projectors