Screens are sold by their diagonal, which is the one measurement that tells you almost nothing useful. A 55-inch set is 48 inches wide in 16:9 and quite different in 21:9, and the diagonal hides the fact that going from 55 to 65 adds forty per cent more picture rather than eighteen. This calculator turns a diagonal and an aspect ratio into real width, height and area, then answers the question that follows: where should the sofa go. SMPTE's reference seat fills 30 degrees of your field of view and THX's cinema figure 40, and both are given in feet or metres. Pixel density and the distance at which pixels stop being resolvable come along too.
Features
Width, height and screen area from any diagonal and aspect ratio
16:9, 21:9, 32:9, 4:3, 16:10 and 3:2 ratios
Recommended viewing distances at the THX, mixed-use and SMPTE angles
Field of view your current seating distance actually gives
The screen size that best fits a distance you already have
Pixel density and the distance at which pixels stop being visible
Side-by-side comparison of two sizes by area and width
Inches or centimetres throughout
How to use the TV Size Calculator
Enter the screen diagonal and pick the aspect ratio
Read the real width and height, and add the bezel when checking a cabinet
Enter your seating distance to see the field of view it gives
Compare against another size to see how much more picture it buys
Example
Input
55 inches, 16:9
Output
47.9 in wide × 27.0 in tall · THX seat 5.5 ft · SMPTE seat 7.4 ft
A 65-inch set in the same ratio has 40% more screen area, not 18%.
Common errors & troubleshooting
The TV does not fit the cabinet despite the numbers. — The figures here are the picture, not the chassis. Add the bezel and the stand — most sets are an inch or two wider than their screen and quite a bit taller.
The recommended distance seems very close. — The THX figure is cinema seating and fills 40 degrees of vision, which many people find too immersive at home. The SMPTE figure at 30 degrees is the conservative end.
An ultrawide monitor gives an odd height. — That is the ratio doing its work. A 34-inch 21:9 screen is only about 13 inches tall, which is why it looks so different from a 34-inch 16:9 panel would.
The pixel density figure looks low for a 4K set. — Spread over 55 inches, 4K is about 80 pixels per inch — lower than a phone by a wide margin. What matters is the viewing distance, which is why the retina figure is shown next to it.
Frequently asked questions
How wide is a 55-inch TV?
About 47.9 inches, or 122 cm, of picture in 16:9, with a height of 27 inches or 68 cm. The chassis is usually an inch or so wider on each side, depending on the bezel.
How far should I sit from a 65-inch TV?
Roughly 6.5 feet at the THX cinema angle and 8.8 feet at the SMPTE reference — so most rooms with a sofa somewhere between seven and nine feet are well suited to a 65.
Is a bigger screen always better for 4K?
Up to the point where you can see the pixels, yes, and 4K pushes that point much closer than 1080p did. The retina distance shown here is where individual pixels stop being resolvable at normal eyesight.
How much more picture does a 65-inch give over a 55?
About 40 per cent more area, because area scales with the square of the diagonal. That is why the jump feels much larger than the ten-inch difference in the name suggests.
Does aspect ratio change the screen area for the same diagonal?
Yes, and by a lot. For one diagonal, the closer the ratio is to square the greater the area — a 4:3 screen has roughly a fifth more area than a 16:9 one of the same diagonal.
Related tools
Aspect Ratio Calculator — Simplify ratios, solve missing dimensions and fit sizes into boxes, with CSS output.
Pizza Size Calculator — Compare pizzas by area and price per square inch, and size an order for a group.