acalculator

What TV size is right for my room?

Type how far you sit from the screen. The calculator gives the 16:9 TV size that fills a 30° viewing angle (SMPTE, the smallest it recommends) and a 40° angle (THX, cinema-like). Add a TV size to see the angle it gives you.

Your numbers

Units
Smallest size (SMPTE, 30°)
59 in

At 8 ft, a TV of 59 in fills 30° of your view; 80.2 in fills 40°.

Cinema size (THX, 40°)
80.2 in
SMPTE screen width
51.4 in

Smallest size (SMPTE, 30°): 59 in. At 8 ft, a TV of 59 in fills 30° of your view; 80.2 in fills 40°.

How to calculate

Recommends a TV screen size for your viewing distance from the SMPTE 30° and THX 40° viewing angles, and shows the viewing angle of a TV you already have in mind.

Example with the default inputs (Viewing distance 8 ft): At 8 ft, a TV of 59 in fills 30° of your view; 80.2 in fills 40°.

Method: Screen width = 2 × distance × tan(angle ÷ 2), at 30° (SMPTE) and 40° (THX); diagonal = width × √(16² + 9²) ÷ 16.

  • The TV is 16:9, as almost all TVs are, and you sit straight in front of the screen.
  • The size is the diagonal of the visible picture, as TVs are sold.
  • SMPTE’s 30° is a smallest comfortable size for a room; THX’s 40° is a cinema-like size.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Viewing distance 8 ft gives Smallest size (SMPTE, 30°) 59 in, Cinema size (THX, 40°) 80.2 in.Source: Optimum HDTV viewing distance, Wikipedia (SMPTE: the screen should fill at least a 30° field of view; THX: about 40°), https://en.wikipedia.org/wiki/Optimum_HDTV_viewing_distance (retrieved 2026-10-03)
  2. Viewing distance 9.843 ft, A TV you are looking at 65 in gives Smallest size (SMPTE, 30°) 72.6 in, Your TV’s viewing angle 26.972888, Your TV Smaller than SMPTE’s 30°: a bigger TV or a closer seat fills more of your view.Source: Optimum HDTV viewing distance, Wikipedia (SMPTE: the screen should fill at least a 30° field of view; THX: about 40°), https://en.wikipedia.org/wiki/Optimum_HDTV_viewing_distance (retrieved 2026-10-03)

How it works

A screen of width W, seen from distance d straight in front of its middle, fills the angle θ = 2 × arctan(W ÷ (2d)). Turned round, the width that fills θ is:

  • W = 2 × d × tan(θ ÷ 2)

For a 16:9 TV, the diagonal is D = W × √(16² + 9²) ÷ 16 = W × √337 ÷ 16.

  • Smallest size (SMPTE): θ = 30°.
  • Cinema size (THX): θ = 40°.
  • Your TV: for a typed diagonal D, W = D × 16 ÷ √337 and the angle is 2 × arctan(W ÷ (2d)), in degrees, shown to 1 decimal. The verdict reads the angle as shown (rounded to 1 decimal): below 30.0° is smaller than SMPTE; 30.0° to 40.0° (both included) is in the recommended range; above 40.0° is wider than THX.

Rules

  • The distance is 1 ft to 100 ft, in feet, inches, meters or centimeters; the TV size 1 in to 1,000 in, in inches or centimeters.
  • Sizes show in inches in US units and centimeters in Metric.

Worked examples by hand

8 ft (96 in). SMPTE: W = 2 × 96 × tan 15° = 51.45 in; D = 51.45 × 18.358 ÷ 16 = 59.0 in. THX: W = 2 × 96 × tan 20° = 69.88 in; D = 80.2 in.

3 m with a 65 in TV. SMPTE: W = 2 × 300 × tan 15° = 160.77 cm; D = 184.5 cm (72.6 in). The 65 in TV is 65 × 2.54 × 16 ÷ 18.358 = 143.9 cm wide, so its angle is 2 × arctan(143.9 ÷ 600) = 27.0°, smaller than SMPTE’s 30°.

Other questions people ask

What size TV should I get for 8 feet?

At 8 ft (96 in), a 59 in TV fills 30° of your view (SMPTE) and an 80 in TV fills 40° (THX). A 65 in or 75 in TV sits between the two.

What are the SMPTE and THX recommendations?

SMPTE, the film and television engineers’ society, recommends that the screen fills at least a 30° field of view. THX, which certifies cinemas and home theaters, recommends about 40° for an immersive picture.

How is the TV size worked out from the angle?

A screen that fills an angle θ at distance d is 2 × d × tan(θ ÷ 2) wide. A 16:9 screen’s diagonal is its width × √(16² + 9²) ÷ 16, about 1.147 times the width.

How far should I sit from a 65 inch TV?

A 65 in TV is 56.7 in wide. It fills 40° at 56.7 ÷ (2 × tan 20°) = 77.8 in (6.5 ft) and 30° at 56.7 ÷ (2 × tan 15°) = 105.7 in (8.8 ft).

Does 4K let me sit closer?

Yes. A sharper picture lets you sit closer before you see the pixels, so a 4K TV can fill the larger THX angle without looking soft. The angles here are about comfort and immersion, not resolution.

Where do I measure the distance from?

From your eyes, where you usually sit, to the screen.