Projector Screen Size and Viewing Distance Calculator
What size projector screen you need for your seat, and how far to sit from the screen you have, against SMPTE, THX and RP22, with the brightness it needs.
For a 120 in 16:9 screen, sit between 2.30 m and 3.29 m from it (RP22, 44 to 60 degrees); your seat at 3.60 m sees 40.5 degrees. The JVC DLA-NZ7 fills it 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.
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.
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.
What size projector screen do I need?
Start from where you sit. Measure from your eyes, in your seat, to the wall the screen goes on. The right screen is the one that fills a comfortable part of your view from there, which the standards describe as a horizontal viewing angle:
- 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 16:9 screen, that gives:
| Eyes to screen | THX 36 degrees | RP22 44 degrees | RP22 60 degrees |
|---|---|---|---|
| 2.5 m (8 ft 2 in) | 73 in | 91 in | 130 in |
| 3.0 m (9 ft 10 in) | 88 in | 110 in | 156 in |
| 3.5 m (11 ft 6 in) | 103 in | 128 in | 183 in |
| 4.0 m (13 ft 1 in) | 117 in | 146 in | 209 in |
Those are the sizes at which the screen fills exactly that angle: at least the THX size for THX, and anything between the two RP22 columns for RP22. The calculator above works it out for your seat, your aspect ratio and your screen, and prints the angle you get.
How far should I sit from a projector screen?
If the screen is already chosen, turn it around. For a 16:9 screen, RP22’s 44 to 60 degrees is between 0.87 and 1.24 times the screen width away. THX’s 36 degrees is 1.54 times the width, and SMPTE’s 30 degrees 1.87 times.
- 100 in: RP22 1.92 to 2.74 m; THX 3.41 m or closer.
- 120 in: RP22 2.30 to 3.29 m; THX 4.09 m or closer.
- 150 in: RP22 2.88 to 4.11 m; THX 5.11 m or closer.
Rules of thumb such as “1.5 times the width” land near THX (about 37 degrees) and well behind RP22. They are rough versions of the same angle; the angle is the thing to check.
Measuring your room
Three measurements settle most of it:
- Eyes to screen wall, from the main seat, sitting down. This is the viewing distance the angles are measured at. If the screen will stand forward of the wall (a floating frame, or an acoustically transparent screen with speakers behind it), measure to where the screen will be.
- Wall width available for the screen, leaving room for the left and right speakers beside it if they are not behind an acoustically transparent screen.
- Ceiling height and the height of the screen’s bottom edge: a tall 16:9 screen low enough for the back row to see over the front row may not fit under a low ceiling. The calculator lowers the screen to fit under the ceiling you give it and tells you when it cannot.
The calculator takes the seat distance first on this page. Change the screen size and aspect ratio and watch the angle and the standards’ verdicts move.
Rows, sightlines and the second seat
A home cinema or home theater usually has more than one seat. The rear row sees a smaller angle than the front: with a 120 in screen, a front row at 2.5 m is at 56 degrees, and a second row 1.3 m behind it at 38.5 degrees, inside THX but outside RP22. A bigger screen helps the back row and can push the front row past 60 degrees, so the usual answer is to size for the main seat and accept that the back row is further out.
The rear row also has to see over the heads in front. That needs a riser, a higher screen, or both, and depends on seat heights and the screen’s bottom edge. The Cinema Designer checks every seat’s angle and the sightline over the row in front.
Brightness sets the upper limit
A bigger screen spreads the same light over more area. Going from 120 in to 150 in, same aspect, needs 56% more light to look as bright. The targets:
- SDR: 48 to 55 nits (14 to 16 fL), the SMPTE cinema reference, and up to about 75 nits in a dark room.
- HDR: 108 nits (31.5 fL), the Dolby Cinema level; 69 to 108 nits is limited.
Use measured lumens, not the maker’s rating. JVC rates the DLA-NZ7 at 2,200 lumens; ProjectorCentral measured 1,609 in its calibrated-for-SDR Cinema mode at the widest zoom. The calculator prints the brightness at every size from 100 to 200 in for the projector and screen material you choose, so you can see where the picture drops out of the HDR range.
Aspect ratio: 16:9 or scope
The standards measure the horizontal angle, so what counts is screen width, not the diagonal. A 2.40:1 scope screen is wider than a 16:9 screen of the same diagonal, so it reaches the same angle from further back. On a scope screen, 16:9 material is shown narrower with bars at the sides, and films in 2.39:1 fill it. If you watch mostly films, size the scope screen’s width to your seat; if you watch mostly television and games, size a 16:9 screen.
Then place the projector
Once the screen size is settled, the projector’s throw ratio and lens shift decide where it can go: the calculator prints the throw window, the lens height window and the light on screen for the eight projectors in openavdb or any model you type in. Continue in Cinema Designer opens your screen, seat and projector in a full room with speakers placed around you, to check sightlines, speaker angles and bass together.