TV Size and Viewing Distance Calculator
Enter how far you sit to get the TV size that fits, or enter your TV size to get the best seat distance, the viewing angle, and whether you'll see the 4K detail.
30° follows the SMPTE guideline for mixed viewing; 40° is the THX guideline for a cinema feel. They are guidelines, not rules.
Typical on a sofa: about 42 in (107 cm).
Common TV sizes and where to sit
| Size | Width × height | Cinema 40° | Everyday 30° | 4K pixels vanish |
|---|
How your TV size is worked out
Pick a viewing angle, find the screen width that fills it, then check the pixels.
- 1
Pick the angle
Everyday (SMPTE)
= 30° - 2
Width that fills it
2 × 96 × tan 15°
= 51.4 in - 3
Width to diagonal
51.4 × 18.36 ÷ 16
= 59.0 in - 4
Check the pixels
55 in 4K pixels
vanish past 3.6 ft
→ Not visible
Read more: the formula, a worked example, the guidelines and mounting height
How big a TV looks depends on two things: its width and how far away you sit. Together they set the viewing angle, the slice of your view the screen fills. Industry guidelines suggest an angle, and the calculator turns that into a size or a distance. Your own eyes, room and taste matter too, so treat the answers as a starting point.
The formula
screen width = diagonal × 16 ÷ √(16² + 9²) = diagonal × 0.8716 (16:9)
screen height = diagonal × 9 ÷ √(16² + 9²) = diagonal × 0.4903
viewing angle = 2 × arctan(width ÷ (2 × distance))
width for an angle = 2 × distance × tan(angle ÷ 2)
distance for an angle = width ÷ (2 × tan(angle ÷ 2))
pixels vanish beyond = (height ÷ pixel rows) ÷ tan(1 arcminute)
For 21:9 use 21 and 9 in place of 16 and 9, and for 4:3 use 4 and 3. Pixel rows are 1,080 for 1080p, 2,160 for 4K and 4,320 for 8K.
Worked example
You sit 8 ft (96 in) from the screen and want the everyday 30° angle. The width that fills 30° is 2 × 96 × tan 15° = 2 × 96 × 0.26795 = 51.45 in. A 16:9 screen's diagonal is its width × 18.358 ÷ 16, so 51.45 × 1.1474 = 59.0 in (150 cm). The nearest common sizes are 55 in and 65 in; 55 in is closer.
A 55 in TV is 55 × 0.8716 = 47.9 in wide and 55 × 0.4903 = 27.0 in tall. From 8 ft it fills 2 × arctan(47.9 ÷ 192) = 28.0°. Each 4K pixel is 27.0 ÷ 2,160 = 0.0125 in tall, and the eye (20/20 vision) stops seeing it beyond 0.0125 ÷ 0.000291 = 43 in, or 3.6 ft. The 1080p limit is twice that, 7.2 ft. You sit at 8 ft, beyond both, so a 4K picture won't look sharper than 1080p from there: sit closer than 7.2 ft, or go bigger, to see the extra detail.
For the cinema feel (40°) at 8 ft: 2 × 96 × tan 20° = 69.9 in wide, a diagonal of 69.9 × 1.1474 = 80.2 in.
The guidelines
| Guideline | Angle | Distance ≈ diagonal × |
|---|---|---|
| SMPTE (mixed use) | 30° | 1.63 |
| THX minimum (back row) | 36° | 1.34 |
| THX (cinema feel) | 40° | 1.20 |
The multipliers are for 16:9 screens. SMPTE's EG-18 guideline asks for at least about 30°; THX recommends about 40° for the best seats and 36° for the back row of its certified cinemas. Many reviewers, such as RTINGS, suggest about 40° for 4K TVs.
Mounting height
Put the centre of the screen at your seated eye level so you look straight ahead. A typical seated eye height on a sofa is about 42 in (107 cm). Bottom edge = eye height − screen height ÷ 2. For a 65 in TV (31.9 in tall): 42 − 15.9 = 26.1 in (66 cm) from the floor, and the top edge is at 57.9 in (147 cm). The TV body is usually 1–3 cm bigger than the screen on each side, so leave a little extra room on the wall.
Guidelines checked 2026-10-13. Visual acuity of 1 arcminute is 20/20 vision; younger or sharper eyes see a bit more, older eyes a bit less.
Common questions
What size TV should I get for my room?
Measure from your eyes to the screen, then use a viewing angle. For everyday TV, a 30° angle (the SMPTE guideline) works well: at 8 ft (2.44 m) that is a screen of about 59 in, so a 55 or 65 in TV. For a cinema feel, THX suggests about 40°, which at 8 ft is about 80 in. These are guidelines; comfort and taste vary.
How far should I sit from a 65 inch TV?
A 65 in 16:9 TV is 56.7 in wide. For a 40° cinema view (THX) sit about 6.5 ft (2 m) away; for a 30° mixed-use view (SMPTE) about 8.8 ft (2.7 m). With 20/20 vision you can see single 4K pixels only from closer than about 4.2 ft, and 1080p pixels from closer than about 8.5 ft.
Is 4K worth it at my viewing distance?
Only if you sit close enough to see the extra detail. With 20/20 vision the eye resolves about 1 arcminute. If you sit farther than the distance where 1080p pixels disappear, a 4K picture looks about as sharp as 1080p. For a 55 in TV that is about 7.2 ft (2.2 m). 4K still often brings better HDR, colour and processing.
How high should I mount my TV?
Put the centre of the screen at your seated eye level, which is typically about 42 in (107 cm) from the floor on a standard sofa. For a 65 in TV that puts the bottom edge about 26 in (66 cm) up. Mounting much higher, like above a fireplace, means tilting your head up; tilt the TV down if you must.
What is the difference between the THX and SMPTE guidelines?
Both are based on how wide the screen looks from your seat. SMPTE (the Society of Motion Picture and Television Engineers) suggests the screen fill at least about 30° of your view. THX recommends about 40° for an immersive, cinema-like picture, and at least 36° from the back row of a THX-certified cinema. A wider angle means a bigger TV or sitting closer.
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