TV size and viewing distance calculator
Divide your seat-to-screen distance in inches by about 1.6 for a relaxed 30 degree view, or by 1.2 for a cinema-style 40 degree view. From 9 ft away that means a 66 to 90 inch 16:9 TV; most people land near 75 inches. 4K detail is fully visible within about 4 ft of a 65 inch set.
Updated · By the Interior Redesign AI editorial team · Sources cited on the page
The eye height default of 40 in is our assumption: measure yours on the sofa. TV sizes are sold in inches everywhere, so the size stays in inches.
TV size for your seat
66-90 in
30° (SMPTE, relaxed) to 40° (THX, cinema) from 9 ft.
| 30° viewing angle (SMPTE) | 66 in |
|---|---|
| 40° viewing angle (THX) | 90 in |
| 4K full detail from here (ITU 1.6 H) | 138 in or larger |
| 1080p looks sharp up to (ITU 3.2 H) | 69 in |
| Screen center no higher than | 69 in |
Viewing angles are guidance for a 16:9 screen, not rules. The height limit keeps your line of sight within 15° of eye level, per Toshiba's TV guide.
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Key numbers
- SMPTE EG 18 (cinemas, withdrawn 2003)
- Under about 30° the image looks small: seat at most about 1.63 × the diagonal away
- THX best seat
- About 40°: seat about 1.2 × the diagonal away
- 1080p full detail (ITU-R BT.1845-1)
- 3.2 picture heights, about 1.57 × the diagonal
- 4K full detail (ITU-R BT.1845-1)
- 1.6 picture heights, about 0.78 × the diagonal
- Mounting height
- Keep the line of sight within 15° of eye level (Toshiba)
- 16:9 screen width
- 0.872 × the diagonal; height 0.49 × the diagonal
Worked example
A sofa 9 ft from the wall
The seat is 108 in from the screen and you want to choose between a relaxed and an immersive size.
- 30° (SMPTE): 2 × 108 × tan(15°) ÷ 0.872 = 66 in diagonal.
- 40° (THX): 2 × 108 × tan(20°) ÷ 0.872 = 90 in diagonal.
- Full 4K detail at 108 in needs a screen about 138 in (108 ÷ 1.6 picture heights), so any size in the range looks sharp, not pixelated.
- Screen center: with a 40 in eye height, keep it at or below about 69 in from the floor (15° up).
Pick a TV between 66 and 90 in; a 75 in set sits in the middle of that range.
How we calculate
A 16:9 screen is 0.872 times its diagonal wide. A screen of width W seen from distance d fills a horizontal angle of 2 × atan(W ÷ 2d). We solve that for the two angles most guides use: 30 degrees, the point below which SMPTE's cinema guideline EG 18 says an image looks small (written for theaters and withdrawn in 2003, but still the source of the figure), and 40 degrees, the angle THX gives for the best seat. THX's own page refuses automated checks, so we cite a summary of its rule and Toshiba's TV guide, which also uses 40 degrees.
For detail, ITU-R Recommendation BT.1845-1 sets the optimal distance where neighboring pixels are 1 arc-minute apart: 3.2 picture heights for 1080p and 1.6 for 4K. Farther back than that, the eye cannot resolve every pixel, which is why 4K looks like 1080p from across a typical living room.
For height, we apply Toshiba's guidance to keep the vertical line of sight within 15 degrees. Your seated eye height is an input: measure it, since it depends on you and the sofa. The default of 40 in is our assumption, not a published figure.
Estimates, sources
Planning estimates and published guidelines, not quotes, designs or code rulings. Figures were checked on each source on the date shown. Local prices, your home and your jurisdiction's adopted code decide the real answer.
- EG 18-1994: Design of Effective Cine Theaters (withdrawn March 26, 2003) (Society of Motion Picture and Television Engineers (SMPTE), as of Oct 26, 2026): section 3: the image will appear small if it occupies less than 15° of the viewer's vertical field of vision or approximately 30° of the horizontal field; written for cinemas and withdrawn in 2003, SMPTE now offers it as an archived reference
- Optimum HDTV viewing distance (summary of THX guidance, secondary) (Wikipedia, as of Oct 26, 2026): THX: best seat at about 40° horizontal (about 1.2 × the diagonal for 16:9). Secondary source: THX's own FAQ refuses automated fetching, and its search listing gives the same rule as screen size = distance × 0.835
- Recommended TV viewing distance (Toshiba Research Center) (Dynabook Americas (Toshiba), as of Oct 26, 2026): keep the horizontal sight line to the screen within 40° and the vertical line of sight within 15°
- Recommendation ITU-R BT.1845-1: metrics for image quality levels, display sizes and aspect ratios (International Telecommunication Union (ITU-R), as of Oct 26, 2026): optimal viewing distance = where adjacent pixels subtend 1 arc-min; 1920 × 1080: 31°, 3.2 H; 3840 × 2160: 58°, 1.6 H (H = picture height)
Viewing distance by TV size
Distances for common 16:9 sizes. Sit between the 40° and 30° columns; the 4K column is how close you must sit to see every pixel of a 4K picture.
| TV size | 40° (THX) | 30° (SMPTE) | 4K full detail |
|---|---|---|---|
| 43 in | 4.3 ft | 5.8 ft | 2.8 ft |
| 50 in | 5 ft | 6.8 ft | 3.3 ft |
| 55 in | 5.5 ft | 7.5 ft | 3.6 ft |
| 65 in | 6.5 ft | 8.8 ft | 4.2 ft |
| 75 in | 7.5 ft | 10.2 ft | 4.9 ft |
| 85 in | 8.5 ft | 11.5 ft | 5.6 ft |
| 98 in | 9.8 ft | 13.3 ft | 6.4 ft |
How high to mount the TV
Toshiba's guide keeps the vertical line of sight within 15 degrees. From 8.8 ft away with a 40 in eye height, that puts the center of the screen no higher than about 68 in. A TV over a fireplace usually sits higher than that, which is why it can feel like the front row at the movies.
A tilting mount helps when the screen has to go higher, because it keeps the screen facing your eyes.
How to use this tool
Measure the distance
From your eyes in the main seat to where the screen will hang.
Read the size range
The 30° and 40° sizes bracket a comfortable to immersive screen.
Check detail and height
See whether 4K detail is visible from your seat and how high the screen center can go.
Questions
What size TV should I get for my room?
Divide the seat distance in inches by 1.63 for a 30 degree view or 1.2 for a 40 degree view. From 8 ft (96 in) that is about 59 to 80 inches.
How far should I sit from a 65 inch TV?
About 6.5 ft for THX's 40 degrees and 8.8 ft for SMPTE's 30 degrees. Anywhere in between is comfortable.
Does 4K change how close I can sit?
Yes. ITU-R BT.1845-1 puts full 4K detail at 1.6 picture heights, half the 3.2 for 1080p, so you can sit closer without seeing pixels. From farther back, extra resolution is hard to see.
Is bigger always better?
Not past 40 degrees. A screen that fills more of your view makes you turn your head to follow action, and subtitles and scores sit at the edges.
How high should a TV be mounted?
Near seated eye level. Toshiba's guide keeps the vertical line of sight within 15 degrees, so measure your eye height on the sofa and keep the screen center near it.
Do these rules work for ultrawide or 4:3 screens?
The math here assumes 16:9, which almost all TVs use. For other shapes, compare screen widths, not diagonals.
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