Choose the perfect TV size for your room. Calculate the ideal diagonal based on your viewing distance and field of view for a theater-like experience at home.
The TV Size Calculator does the reverse of the viewing distance tool: enter how far the seating is from the wall and it returns the recommended diagonal in inches for both THX and SMPTE viewing standards. It is the right starting point when the couch position is fixed and you need to know which TV size will fill the field of view correctly for a 16:9 panel.
Given a seating distance D, the calculator solves screen width = 2 x D x tan(half-angle), then converts width to diagonal using diagonal = width / cos(arctan(9/16)). THX uses a 36 degree angle (half-angle 18 degrees) and SMPTE EG-18 uses 30 degrees (half-angle 15 degrees). At a 10 ft viewing distance, this yields about 92 inches for THX and 75 inches for SMPTE.
Measure your viewing distance — the distance from your seating position to where the front of the TV will be. Enter this in feet or meters. The calculator returns two TV size recommendations based on industry standards.
THX recommends the larger size (36° viewing angle) for an immersive, cinema-like experience. SMPTE recommends a slightly smaller size (30° angle) for comfortable everyday viewing without eye fatigue.
Most people find the ideal TV size falls between the THX and SMPTE recommendations. For 4K content, you can safely go with the larger THX recommendation since individual pixels won't be visible at that distance.
At 10 ft, THX (36 degrees) recommends roughly a 92-inch diagonal and SMPTE EG-18 (30 degrees) recommends roughly 75 inches for a 16:9 TV. A 77 to 85-inch panel typically sits in the comfort zone between the two standards.
For 8 ft, the THX target is about 73 inches and the SMPTE target is about 60 inches. A 65 to 75-inch 4K TV is the sweet spot for most living rooms with that distance.
Yes. Once the horizontal viewing angle exceeds about 40 degrees, the eye has to scan to take in the picture, causing fatigue. THX caps the comfortable maximum at 36 degrees and SMPTE caps it at 30 degrees, so anything wider should be reserved for short cinematic sessions.
Yes. Wider aspect ratios such as 21:9 produce a shorter screen for the same diagonal, so for the same viewing angle you would need a larger diagonal. The calculator assumes a 16:9 panel, which covers virtually all modern TVs.
For a 7 to 9 ft viewing distance, 65 inches sits between the SMPTE and THX recommendations and is widely considered the modern living-room sweet spot. Below 7 ft a 55-inch is fine, and above 10 ft you should step up to 75 inches or larger.