Viewing distance calculator
Where to put the sofa, or the camping chairs, for your screen: by the viewing angles SMPTE and THX give and by the distance at which your eyes can still pick out every pixel.
1From your screen
Sit between 1.98 m and 2.21 m for THX's view, and no farther than 2.69 m6 ft 6 in to 7 ft 3 in; no farther than 8 ft 10 in
| Guideline | Distance |
|---|---|
| SMPTE: farthest seat (30°)Beyond this the picture fills less than 30° of your view and starts to look small. | 2.69 m8 ft 10 in |
| THX: farthest seat (36°)THX's figure for the back row of a well-designed room. | 2.21 m7 ft 3 in |
| THX: about 40° (rule of thumb)From THX's "screen size = distance × 0.835" rule; a big, immersive picture. | 1.98 m6 ft 6 in |
| Resolution: 4K UHD (1 arc-minute)Adjacent pixels are 1 arc-minute apart here (ITU-R BT.2022). Much farther back, the extra detail of this resolution is lost. | 1.29 m4 ft 3 in |
1 arc-minute distances for other resolutions: 720p HD 3.86 m · 1080p Full HD 2.58 m · 4K UHD 1.29 m · 8K UHD 64 cm.
2Or start from your seat
| Guideline | Screen size |
|---|---|
| SMPTE minimum (30°) | 73 in (184 cm) |
| THX back row (36°) | 88 in (224 cm) |
| THX rule of thumb (about 40°) | 99 in (251 cm) |
| Full detail of 1080p Full HD | 76 in (192 cm) |
| Full detail of 4K UHD | 151 in (384 cm) |
| Full detail of 8K UHD | 303 in (769 cm) |
How it works
The angle a screen fills depends on its width and how far away you sit: a picture W wide seen from D away fills 2 × arctan(W ÷ 2D). Turn that round and the distance for an angle θ is (W ÷ 2) ÷ tan(θ ÷ 2).
SMPTE's cinema design guideline asked for the picture to fill about 30° of the view of the most distant seat, which works out at about 1.87 times the picture width. THX recommends a 36° angle from the farthest seat (about 1.54 widths), and its rule of thumb of buying a screen whose diagonal is 0.835 times your seating distance comes to about 40° on a 16:9 screen (about 1.37 widths). Sitting anywhere in that range feels like a cinema.
The resolution distance comes from ITU-R BT.2022: the distance at which neighbouring pixels are one arc-minute (1/60 of a degree) apart. For a 16:9 screen that is 3.2 picture heights for 1080p, 1.6 for 4K and 0.8 for 8K. Sit much farther back than this and the extra pixels of a sharper format are wasted.
For screens wider or narrower than 16:9, the calculator assumes the picture uses the full width (wider screens) or full height (narrower ones) of the video's 16:9 pixel grid.
Sources
- About 30° of the most distant viewer's horizontal field of vision, no more than 35° up to the top of the picture from the nearest seat, and the angle formula: SMPTE EG 18-1994, Design of Effective Cine Theaters. SMPTE withdrew this guideline in 2003 and keeps it as an archived reference.
- 36° from the farthest seat, and screen size ≈ seating distance × 0.835: THX's FAQ and What size TV should I buy for my living room?
- Design viewing distance where two adjacent pixels subtend 1 arc-minute, with 4.8H (720p), 3.2H (1080p), 1.6H (4K) and 0.8H (8K): Recommendation ITU-R BT.2022, Table 1.
Questions
Which distance should I use?
For a cinema feel, seat people between the THX distances and no farther back than the SMPTE one. Check the resolution line too: if your seats are much farther away than it, a sharper screen won't look any different from there.
How close is too close?
Closer than the resolution distance you may start to see the pixels, and you have to turn your head to follow the action. SMPTE's guideline also says the top of the picture should be no more than 35° above eye level from the nearest seat, or necks start to ache.
Does this work for an outdoor screen?
Yes. Enter the picture's diagonal, and the distances tell you where the front and back rows of blankets should go. A big outdoor screen means a large seating area, so check the back row against the SMPTE distance.