Projector Screen Size Calculator
A projector’s picture width is the throw distance divided by the throw ratio. Enter both, and this works out the width, height and diagonal, plus where to sit.
How do you work out a projector’s screen size?
Divide the throw distance by the throw ratio to get the picture width. The screen shape then sets the height, and the diagonal follows from both.
So a projector with a throw ratio of 1.5, placed 10 ft (3.05 m) from the wall, makes a 16:9 picture 80.0 in203.2 cm wide. Its diagonal is 91.8 in233.1 cm.
What is a throw ratio?
It is the throw distance divided by the picture width, as printed on the projector’s spec sheet. A lower number makes a bigger picture from the same spot.
A projector with a zoom lens lists two numbers. The picture is largest at the smaller one, so a zoom gives you some room to move the projector.
How far should a projector be from a 100 inch screen?
For a 100 inch (254 cm) 16:9 screen, it depends on the throw ratio. At 1.2 it is 8.7 ft2.7 m, at 1.5 it is 10.9 ft3.3 m, and at 2.0 it is 14.5 ft4.4 m.
The table shows the distance for more sizes, measured from the lens.
Where should I sit for a projector screen?
Sit where the picture fills 30 to 40 degrees of your view, the same rule as for a TV. For a 100 inch 16:9 screen, that is 10.0 ft3.0 m to 13.6 ft4.1 m away.
Closer than that, you have to turn your head to follow the action. Further back, the picture starts to look small.
Which screen shape should I choose?
Pick the shape of what you watch most, so the picture fills the screen.
- 16:9 suits TV, streaming, sport and games.
- 16:10 suits laptops and slides made for them.
- 4:3 suits older films, TV shows and some classroom slides.
- 2.35:1 suits widescreen films with no black bars.
At the same distance, a 2.35:1 picture is as wide as a 16:9 one but only 34.0 in86.5 cm tall.
Why is my picture a different size from the result?
The zoom setting is the usual cause, so check where it sits. Keystone correction also shrinks the picture when the projector is not square to the screen.
Measure from the lens to the screen unless your manual says otherwise.
What do short throw and long throw mean?
They describe how far the projector must sit for a given picture. Makers usually call a projector short throw when its ratio is below about 1.0, and ultra short throw below about 0.4.
For a 100 inch picture, a 0.8 ratio needs only 5.8 ft1.8 m, while a 2.0 ratio needs 14.5 ft4.4 m. A short throw suits small rooms, and a long throw can sit behind the seats.
How big a screen can my wall take?
Measure the clear wall width first, then leave room for the frame and any speakers. A 120 inch 16:9 screen is 104.6 in (265.7 cm)265.7 cm (104.6 in) wide before the frame.
Then check the height. The bottom of the picture should clear furniture and heads in the front row.
Does a bigger screen make the picture dimmer?
Yes. The projector spreads the same light over more area, so every part of the picture gets less of it. A 120 inch screen has 44% more area than a 100 inch one, so it looks dimmer from the same projector.
In a bright room, a smaller screen or a brighter projector helps more than a bigger picture.
How do I set up a projector step by step?
Plan the screen first and the projector second. These steps work for most rooms:
- Measure from your main seat to the screen wall, and pick a size from the seating rule above.
- Look up your projector’s throw ratio on its spec sheet.
- Enter the size and ratio in the second calculator to get the throw distance.
- Mark that distance from the wall, on a shelf, table or ceiling mount.
- Fine-tune the size with the zoom, and the position with lens shift if you have it.
What should I look for in a projector screen?
The screen matters almost as much as the projector. Four things decide how it looks:
- Shape: match your projector’s native shape, usually 16:9.
- Size: use the viewing area, not the frame, when you compare.
- Type: fixed frames stay flat, pull down screens hide away, and portable screens travel.
- Surface: matte white suits dark rooms, while gray surfaces help in rooms with some light.
Where should I put the projector?
Put it where the throw distance lands, on a shelf behind the seats or on a ceiling mount. A ceiling mount keeps the beam above heads and the projector out of reach.
Most projectors aim the picture a little above or below the lens, so check the offset in the manual. Mount it upside down on the ceiling, then use the flip setting to turn the picture the right way up.
What resolution do I need for a big screen?
More pixels matter more as the screen grows, because each pixel gets bigger. Pixels on a 120 inch screen blend into a smooth picture from these distances, for 20/20 vision:
- 1080p: about 15.6 ft4.8 m or more,
- 4K: about 7.8 ft2.4 m or more.
See our guide to resolution vs screen size for how pixel density changes with size.
Should I get a projector or a big TV?
A projector gives the biggest picture for the space, and a TV gives the brightest one. The choice comes down to light and size:
- a projector suits a dark room and a picture over 100 inches (254 cm),
- a TV suits a bright room, daytime sport and gaming,
- a TV needs no screen, throw distance or mount planning.
Compare the size with our 100 inch TV dimensions and the biggest TV sizes on sale.
Can I use the calculator for a pull-down or portable screen?
Yes. The math is the same for any screen type, so enter the throw ratio and distance as usual. Then pick the screen size closest to the result.
A portable screen on legs can move closer or further, so you can match it to the picture. Our projector screen size guide compares the screen types.
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Which screen size should I buy from the result?
Pick the nearest screen size at or just below the result. You can then zoom the lens slightly to fill it exactly.
Where do I find my projector’s throw ratio?
It is on the spec sheet and in the manual, often next to the lens details. A zoom lens has two numbers, and the smaller one gives the bigger picture.
Does a short throw projector change the screen size?
No. It makes the same size picture from closer to the wall, because its throw ratio is lower.
Can I use the calculator in meters?
Yes. Switch the units at the top of the page, and the distance moves to meters and the sizes to centimeters.
What if my projector is not centered on the screen?
Use lens shift if the projector has it, since it moves the picture without changing its size. Keystone correction also squares it up, but it makes the picture smaller.
Does the throw distance include the projector body?
Most makers measure from the front of the lens, but a few measure from the back of the body. Check the manual, since it can move the result by several inches.
Can I use this for a 2.35:1 or 4:3 screen?
Yes. Pick the screen shape, and the height and diagonal change while the width stays set by the distance.
How we measure
Picture width = throw distance ÷ throw ratio. Height = width × b ÷ a for an a:b screen, and the diagonal is √(width² + height²). Seats run from the distance where the width fills 40 degrees of view to where it fills 30.