A short throw projector fills a 100-inch wall from about 1.1 metres, and an ultra short throw unit does it from under half a metre. A traditional 2.0:1 lens needs 4.4 metres for the same picture. The throw ratio on the spec sheet decides it, and one line of arithmetic checks your room.
The one formula: distance equals throw ratio times image width
BenQ defines throw ratio as throw distance divided by image width: a ratio of 2.0 means two feet of distance for every foot of picture. Flip it: distance equals throw ratio multiplied by image width.
Width is not the diagonal. A 16:9 picture is 87 percent as wide as its diagonal, so a 100-inch screen is 2.21 metres wide and a 120-inch one is 2.66.
BenQ’s cut-off for short throw is a 100-inch image from under 3 metres. Epson’s projector buying guide puts short throw at 3 to 8 feet and ultra short throw at 0 to 4 feet.
Four spec sheets, one 100-inch wall
The table applies the formula to four current models using each manufacturer’s published throw ratio. Brightness carries the standard the sheet cites, because a bare lumens figure and an ISO 21118 figure are different claims, as our piece on how projector lumens are rated explains.
| Model | Class | Throw ratio | Lens to wall for 100 in | Brightness as stated | Latency | Weight |
|---|---|---|---|---|---|---|
| Optoma GT2100HDR | Short throw | 0.496:1 | 1.10 m (calculated) | 4,200 lumens, no standard cited | 8.6 ms at 1080p 120 Hz | 3.0 kg |
| XGIMI Horizon S Pro | Standard | 1.2:1 | 2.66 m (calculated) | 1,800 ISO lumens | 20 ms or less, game mode | 4.75 kg |
| XGIMI Aura 2 | Ultra short throw | 0.177:1 | 0.39 m (calculated) | 2,300 ISO lumens | Down to 20 ms | 9 kg |
| Epson Lifestudio Grand Plus | Ultra short throw | 0.16 to 0.40:1 | 0.3 to 0.5 m for 80 to 150 in (published) | 4,000 lumens, ISO 21118:2020 | Not published in ms; 4K 120 Hz with ALLM | 12.5 kg |
One trap in that distance column. XGIMI quotes the Aura 2 at 17.8 centimetres from the wall for 100 inches, yet 0.177 times 2.21 metres is 39 centimetres.
Both are right: the quoted gap runs from the back of the chassis, and the lens sits inside a body 27 centimetres deep. Budget about 45 centimetres of console depth.
Where short throw wins: room depth, shadows, couch gaming
With your seating wall 3 metres from the screen wall, a 1.2:1 lens tops out near 113 inches, a traditional 2.0:1 lens near 68 inches, and the 0.496:1 Optoma GT2100HDR reaches 100 inches from the coffee table.
Epson’s guide also credits short throw with reducing shadows and eye glare, and ultra short throw with virtually eliminating them. Nobody walks between a lens and wall half a metre apart.
For gaming, a projector in front of the couch keeps the HDMI run short, and Optoma lists 8.6 ms input lag at 1080p 120 Hz for the GT2100HDR.
The console-side settings in our guide to reducing input lag on a TV apply unchanged, and any HDMI streamer such as a Fire TV Stick 4K plugs straight in.
What the short and ultra short sheets do not advertise
The Optoma’s zoom is fixed, so image size is set purely by distance. Its 116 percent offset puts the image well above the lens, the panel is 1080p, and the 4,200 lumens carry no measurement standard.
Ultra short throw pays in weight and surface. The Epson Lifestudio Grand Plus weighs 27.5 pounds, uses manual focus, and Epson sells its SilverFlex ambient light rejecting screen separately.
XGIMI’s own footnotes say the Aura 2 wall must be a plain painted surface with no wallpaper, body tilt must stay within 9 degrees, and auto keystone may fail and need manual correction. Its smallest image is 90 inches.
Keystone is not free on any of them. BenQ’s keystone explainer says the corrected side uses only a portion of the pixels, wasting light and resolution as black space. Square placement beats a digital fix.
Standard throw keeps two real advantages. The Horizon S Pro sheet spans 40 to 200 inches, the widest range here, and a ceiling mount behind the seats leaves the coffee table empty. You pay for both in metres.
Frequently asked questions
How far should a short throw projector be from the wall?
Multiply the throw ratio by the image width. At 0.5:1, a 100-inch 16:9 picture needs about 1.1 metres from the lens. At 0.177:1 it needs 39 centimetres, plus the depth of the chassis.
Is a short throw projector faster for gaming than a standard one?
Placement is the gain, not speed. Latency comes from video processing, and the sheets here list 8.6 to 20 milliseconds across all three classes, so read the input lag line, not the throw ratio.
Can I use a short throw projector on a plain wall?
Short throw, yes, on a flat, light-coloured wall. Ultra short throw is fussier: XGIMI requires a plain painted surface with no wallpaper, and Epson pairs its unit with a separately sold ambient light rejecting screen.
Joyce Lewis covers consumer technology, gaming, and online privacy for 3Zebras. She focuses on the practical side of modern tech, from smartphone tips and app guides to smart device security and the questions readers actually search for.