TV viewing distance.

Worked example

Take a 65 inch 16:9 TV. Its width is 65 x 16 / sqrt(16^2 + 9^2) = 56.7 in. A 30 degree view puts you 56.7 / (2 x tan 15 degrees) = 105.7 in (8.8 ft) away, and a 40 degree view puts you 56.7 / (2 x tan 20 degrees) = 77.8 in (6.5 ft) away. The 28 degree far limit is 113.6 in (9.5 ft). For 4K, one pixel is 56.7 / 3840 inches wide, which subtends 1 arcminute at 50.7 in (4.2 ft); sit farther back than that and 4K pixels can no longer be told apart by a 20/20 eye, and for 1080p the same distance is 101.4 in (8.5 ft).

How it works

The distance at which a screen of width W fills a horizontal angle A is W / (2 x tan(A / 2)). For a 16:9 screen the 30 degree distance works out to about 1.626 times the diagonal and the 40 degree distance to about 1.2 times. The Optimum HDTV viewing distance - Wikipedia article reports that a 30 degree view is widely quoted as the SMPTE recommendation but that there seems to be no direct recommendation from SMPTE on the issue, that THX recommends a viewing angle of about 40 degrees as the best seat-to-screen distance, and that THX sets the maximum of its range at about 28 degrees. Treat them as seating guides, not standards you have to meet.

The pixel distances use the 1 arcminute figure that article describes as the usual threshold for telling fine detail apart with normal (20/20) vision. Closer than that distance you can start to see pixel structure; farther away, extra resolution is not visible to that eye. It is a geometry limit, not a picture-quality score.

Sources: Optimum HDTV viewing distance - Wikipedia. Each opened 2026-10-08.

Planning guide only, not professional advice. Figures are estimates from the inputs you enter.

FAQ

How far should I sit from my TV?

A common starting point is a 30 degree to 40 degree view of the screen width. For a 65 inch 16:9 TV that is about 6.5 ft to 8.8 ft. Beyond the 28 degree distance you are outside the THX range.

What is the 30 degree SMPTE rule?

It is the distance at which the screen width fills a 30 degree view, about 1.626 times the diagonal for a 16:9 TV. It is widely quoted as an SMPTE recommendation, but Wikipedia notes there seems to be no direct recommendation from SMPTE on the issue.

What is the THX 40 degree rule?

THX recommends the best seat-to-screen distance is one where the screen fills about 40 degrees, which is the diagonal divided by 0.84, or about 1.2 times the diagonal, for a 1080p picture.

Does a 4K TV let me sit closer?

Yes, geometrically. A 4K panel has twice the pixels across as 1080p, so the distance at which a pixel subtends 1 arcminute is half as large: 4.2 ft against 8.5 ft for a 65 inch TV.

Does this work for curved or ultrawide screens?

It treats the screen as flat. For ultrawide monitors choose the matching aspect ratio, and use the monitor distance calculator for desk use.