Projector Throw Distance and Screen Size Calculator
Where to put your projector for your screen, or what screen fits your throw, with brightness in nits for SDR and HDR, lens shift and seating angle.
The JVC DLA-NZ7 fills a 120 in 16:9 screen from 3.80 m to 7.76 m (12 ft 6 in to 25 ft 5 in). At 5.00 m, it gives 117.7 nits.
Placed inside the throw window; type your own.
Placed at the top of the shift range, below the ceiling.
Empty: the room is sized to fit.
Where the projector goes
- Nearestwidest zoom3.80 m (12 ft 6 in)
- Farthestlongest zoom7.76 m (25 ft 5 in)
- Your throw distanceplaced by the tool5.00 m Fits
- Zoom used1.88:1, 30% into the zoom (1.43 to 2.92:1).1.88:1
- Lens heightFits: the lens sits 80.0% of image height above the image centre; the lens allows the image centre from 80% below to 80% above the lens axis (convention unstated; assumed ±80% of image height from centred).0.25 m to 2.64 m
Light on screen
- SDRBright (75 nits and up); an iris or a lower laser level can trim it. Reference: SMPTE cinema 48 to 55 nits (14 to 16 fL); home dark room to about 75.Bright
- HDRGood (108 to 171 nits). Reference: Dolby Cinema 108 nits (31.5 fL).Good
1,609 lm, Cinema, LD Power High, ProjectorCentral, zoom-adjusted, linear estimate; gain assumed 1.0 (no material chosen); 120 in 16:9, 3.97 m²
Screen: gain assumed 1.0 (no material chosen).
Brightness by screen size
| Diagonal | Nits | fL | SDR | HDR |
|---|---|---|---|---|
| 100 in | 169.5 | 49.5 | Bright | Good |
| 110 in | 140.1 | 40.9 | Bright | Good |
| 120 in (yours) | 117.7 | 34.4 | Bright | Good |
| 135 in | 93.0 | 27.2 | Bright | Limited |
| 150 in | 75.3 | 22.0 | Bright | Limited |
| 175 in | 55.4 | 16.2 | Reference | Short |
| 200 in | 42.4 | 12.4 | Low | Short |
Same lumens and gain as above, same aspect ratio; a model measured over throws is read at your current throw.
Seating
- SMPTE30 degrees or morePass
- THX36 degrees or morePass
- RP2244 to 60 degreesBelow
For this screen, sit between 2.30 m and 3.29 m for RP22 44 to 60 degrees; THX 36 degrees needs 4.09 m or closer; SMPTE 30 degrees needs 4.96 m or closer.
How throw distance works
A projector’s throw ratio is the distance from the lens to the screen divided by the width of the picture. A 1.5:1 lens makes a picture 2 m wide from 3 m away. Most home theater projectors have a zoom lens, so the ratio is a range, and for a given screen you get a window of distances rather than a single point: the nearest at the widest zoom, the farthest at the longest.
Take the JVC DLA-NZ7, with a 1.43 to 2.92:1 zoom, and a 120 in 16:9 screen (2.657 m wide). It fills the screen from 3.80 m to 7.76 m. Put the lens anywhere in that window and zoom until the picture fits. The calculator above does this for the eight projectors in openavdb, and for any other model if you type its throw ratio.
Two things shrink the window in a real room. The projector body sits behind the lens, so the back wall stops the lens short of the wall by the body depth. And zooming costs light on most lenses: the farther back you go, the dimmer the picture (see Brightness, below).
Screen size and seating
How big a screen should be depends on how far you sit from it. The standards describe it as the horizontal viewing angle: how much of your view the picture fills, measured at your eyes.
- SMPTE (ST 2046-1): at least 30 degrees.
- THX: at least 36 degrees.
- RP22 (the CEDIA/CTA home cinema guideline): 44 to 60 degrees for video.
For a 120 in 16:9 screen, 60 degrees is 2.30 m away, 44 degrees is 3.29 m, 36 degrees is 4.09 m and 30 degrees is 4.96 m. So an RP22 seat for that screen is between 2.30 m and 3.29 m.
Rules of thumb like “sit at 1.5 times the screen width” are rough versions of the same idea. 1.5 times the width works out at about 37 degrees, just past THX and well short of RP22. The calculator prints the angle at your seat and the distances for all three standards, for your own screen.
Brightness: lumens, gain and area
The number that matters is how bright the picture looks, measured in nits (candelas per square metre), or in foot-lamberts (fL, 1 fL is 3.426 nits) in older references. It comes from three things:
- Lumens: how much light the projector puts out in the picture mode you watch in.
- Screen gain: how much of it the screen reflects towards you (1.0 is a matte white reference).
- Screen area: the same light spread over a bigger screen is dimmer. Going from 120 in to 150 in, same aspect, needs 56% more light for the same brightness.
The targets the calculator uses:
- SDR: SMPTE cinema reference is 48 to 55 nits (14 to 16 fL). A dark home cinema is comfortable up to about 75 nits; brighter than that, an iris or a lower laser setting can bring it down.
- HDR: Dolby Cinema masters for 108 nits (31.5 fL). The calculator calls 108 nits and up good, 69 to 108 nits limited.
Measured lumens, not the rating. A maker’s figure is usually its brightest, uncalibrated mode at the widest zoom. JVC rates the DLA-NZ7 at 2,200 lumens; ProjectorCentral measured 1,609 lumens in Cinema mode for SDR, and found 28.8% less at the longest zoom. XGIMI rates the TITAN Noir Max at 7,000 lumens (ISO 21118, Performance mode); The Hook Up measured 2,846 lumens with its Dynamic iris. The calculator picks a measured cinema mode by default, lets you choose another picture mode or iris setting, reads a model measured at several throws at your throw, and names the source of every figure it uses.
Lens shift and mount height
Lens shift moves the picture up or down (and on some models sideways) without tilting the projector, so the image stays rectangular with no keystone correction. Each model allows the image centre to sit within a range above or below the lens. Turned around, that gives a window of lens heights that fill your screen: the calculator prints it, clipped to your floor and ceiling.
Ceiling mounts are the common case. If the top of the window is below your ceiling, a ceiling mount needs a drop pole; if the window is empty, the screen height, screen size and ceiling do not work together with that lens. Makers describe shift differently, some as a percentage of picture height each way, some from a default lens position, and the calculator says which convention it read for each model.
Screen gain and material
A screen’s gain compares how much light it returns straight ahead with a matte white reference. Above 1.0, centre seats get a brighter picture and the viewing cone narrows; below 1.0, the picture is dimmer. Ambient-light-rejecting and acoustically transparent materials are often below 1.0.
Rated against measured. XY Screens rates the SoundMAX 4K at gain 1.1; Pixel Home Theater measured 0.79 near on-axis, and 2.1 dB average sound loss through the weave. With openavdb’s 86 screen materials, the calculator uses a measured gain first, then the maker’s rating, and assumes 1.0 when you choose none. Acoustically transparent screens let you put the front speakers behind the picture, which is what cinemas do, at the price of some light and some treble.
When to go further
This page answers one question at a time: where the projector goes, how bright the picture is, and whether the seat suits the screen. A home cinema is those questions together with the speakers, the seats and the room. Continue in Cinema Designer opens a full room with your projector, screen and seat already in it and the speakers placed around you, so you can check sightlines, speaker angles against Dolby and RP22, and bass in the same design.