TV size and viewing distance calculator

What size TV should I get for my room?

THX suggests multiplying your seating distance in inches by 0.835: at 8 feet (96 inches), that is about an 80-inch screen. This fills about 40° of your view with a 16:9 picture.

How far should I sit from a 65-inch TV?

By the THX rule, about 65 ÷ 0.835 = 77.8 inches, or 6 ft 6 in. Sitting farther away makes the picture fill less of your view.

What does the viewing angle mean?

How wide the screen looks from your seat. A larger angle feels more like a cinema; a smaller one is more relaxed. Change the angle to see how the distance changes: at 30°, a 65-inch TV is best from about 8 ft 10 in.

How big is a 65-inch TV?

The size is the diagonal. A 16:9 screen is 0.872 times as wide as its diagonal: a 65-inch TV is about 56.7 × 31.9 inches.

Does resolution change the distance?

Sharper screens let you sit closer before seeing pixels, but the THX guideline is based on viewing angle, not resolution.

How much bigger is a 75-inch TV than a 55-inch?

Compared by diagonal it is 36% larger, but the screen area grows with the square: a 55-inch 16:9 screen is 47.9 × 27.0 inches (1,293 square inches), and a 75-inch is 65.4 × 36.8 inches (2,404 square inches), about 1.86 times the area.

Will it fit on my wall or stand?

Measure the width, not the diagonal. A 75-inch TV is about 65.4 inches wide, which is 5 ft 5 in, plus the bezel and any stand. The stand or mount may also be wider than the screen, so check the width of the stand in the manufacturer's specifications.

How the distance is calculated

The calculator treats the TV as a 16:9 screen and uses the screen width and a viewing angle. The width of a 16:9 screen is 16 ÷ √(16² + 9²) = 0.872 times its diagonal and the height is 0.490 times. For a viewing angle θ the distance is d = (width ÷ 2) ÷ tan(θ ÷ 2): the half-width and the line to your eye form a right triangle. With 40° as the default angle, THX recommends a distance of the screen diagonal ÷ 0.835, which is the shortcut the page shows. A larger angle means sitting closer and a more immersive picture; a smaller angle gives a more relaxed one.

Worked example: a 65-inch TV

A 65-inch 16:9 screen is 56.7 inches wide and 31.9 inches tall. For a 40° viewing angle the distance is 56.7 ÷ 2 ÷ tan(20°) = 77.8 inches, which is 6 ft 6 in. By the THX shortcut, 65 ÷ 0.835 = 77.8 inches, the same result to within rounding. For a narrower 30° angle the distance is 8 ft 10 in. Going the other way, if you sit 8 feet (96 inches) from the screen, the THX factor gives a diagonal of about 80 inches.

Choosing a size in practice

The distance guidance is a starting point, and the room usually sets the limits: the wall width, the seating, window glare and the budget. If you are between two sizes, the larger one is the safer choice for a room with a long viewing distance, and the smaller for a small room with close seating. Seating angle matters as well. Sitting well off to the side makes the effective distance different and, with some panel types, changes the apparent contrast and color. Resolution matters in a different way: a higher-resolution screen lets you sit closer before the pixel structure shows, but the angle-based guidance does not change.

Common mistakes

Treating the advertised size as the width is the first: it is the diagonal, and the width of a 16:9 screen is about 87% of it. The second is measuring the distance to the wall and not to the seat. Third, ultrawide and 21:9 screens have a different shape, so their widths are larger for the same diagonal and the 16:9 calculation does not apply. Finally, a distance in feet and inches must be converted to inches (or the answer read in feet and inches) before applying the 0.835 factor.

Sources: THX's published guidance on viewing distance and a 40-degree viewing angle (distance = screen diagonal ÷ 0.835 for a 16:9 screen); the geometry of a 16:9 rectangle and the tangent function from trigonometry (OpenStax Precalculus). Related: aspect ratio calculator, area calculator and Pythagorean theorem calculator.