How screen size is measured
A screen's size is its diagonal: the distance from one corner of the visible picture to the opposite corner, without the frame. That single number hides the shape. A 34-inch ultrawide and a 34-inch 16:9 monitor have the same diagonal but very different widths and heights, so this screen size calculator always asks for the aspect ratio too.
The math is the Pythagorean theorem. For a 16:9 screen the width is the diagonal × 0.872 and the height is the diagonal × 0.490, so a 65-inch TV is about 56.7 inches wide and 31.9 inches high. For other shapes the calculator uses width = diagonal × W ÷ √(W² + H²). It works as a diagonal screen size calculator in both directions in your head: if a stand is 50 inches wide, any 16:9 TV up to about 57 inches diagonal fits its picture on it, before the frame.
TV and monitor sizes at a glance (16:9)
| Diagonal | Width × height | In cm | Typical use |
|---|---|---|---|
| 24 in | 20.9 × 11.8 in | 53.1 × 29.9 cm | Office and budget gaming monitors |
| 27 in | 23.5 × 13.2 in | 59.8 × 33.6 cm | The most popular desk monitor size |
| 32 in | 27.9 × 15.7 in | 70.8 × 39.8 cm | Large monitors, small TVs |
| 43 in | 37.5 × 21.1 in | 95.2 × 53.5 cm | Bedroom and kitchen TVs |
| 55 in | 47.9 × 27.0 in | 121.8 × 68.5 cm | Living rooms |
| 65 in | 56.7 × 31.9 in | 143.9 × 80.9 cm | Living rooms, the best-selling large size |
| 75 in | 65.4 × 36.8 in | 166.0 × 93.4 cm | Large rooms, home theater |
| 85 in | 74.1 × 41.7 in | 188.2 × 105.8 cm | Home theater |
Size grows faster than the number suggests: a 65-inch TV has about 40% more picture area than a 55-inch one. Use step 1 as a TV screen size calculator for any model, and step 2 as a monitor screen size calculator or TV comparison to see the real difference in width, height and area before you upgrade.
Viewing distance and the right TV size for your room
Two industry guidelines are used as a TV viewing distance calculator. SMPTE recommends that the screen fills about 30° of your view, a relaxed distance for everyday TV. THX recommends about 40° for a cinema-like feel. For a 65-inch 16:9 TV that works out to about 8 ft 10 in (SMPTE) and 6 ft 6 in (THX). As a TV size calculator based on room size, step 3 turns your seating distance into a range: from 8 feet, roughly 59 to 80 inches; from 10 feet, roughly 74 to 100 inches. The same numbers serve as a home theater screen size calculator for projector screens.
Resolution sets the other limit. With normal 20/20 vision you stop seeing single pixels beyond a certain distance; for a 65-inch 4K TV that is about 4 ft 3 in, so from a sofa 8 feet away a 4K picture looks smooth, and a 1080p picture of the same size starts to look soft only when you sit closer than about 8.5 feet.
Pixel density (PPI)
Pick a resolution in step 1 and the page also works as a PPI calculator, or pixel density calculator. PPI is the number of pixels per inch along the diagonal: 24 inches at 1920 × 1080 is 92 PPI, 27 inches at 2560 × 1440 is 109 PPI, and 27 inches at 4K is 163 PPI. Around 90 to 110 PPI looks sharp at a desk without scaling; above that, text is crisper but Windows and macOS usually enlarge it. To see the resolution of the screen you are using now, open the screen resolution checker; to work out the ratio of any width and height, use the aspect ratio calculator.
How we tested this tool
We tested the calculator by script in Google Chrome on Windows. For 16:9 screens of 24, 27, 55 and 65 inches it returned the same widths and heights as the table above (65 inches: 56.65 × 31.87 in), and 165 cm gave the same result as 65 inches. Other shapes were checked too: 34 inches at 3440 × 1440 gave 31.36 × 13.13 in, 49 inches at 32:9 gave 47.17 × 13.27 in, a 13.3-inch 16:10 laptop 11.28 × 7.05 in and a 12.9-inch 4:3 tablet 10.32 × 7.74 in. Pixel density matched the standard figures: 24 inches at 1920 × 1080 is 91.8 PPI, 27 inches at 2560 × 1440 is 108.8 PPI, 34 inches at 3440 × 1440 is 109.7 PPI and 65 inches at 4K is 67.8 PPI. The comparison showed a 65-inch TV with 40% more area than a 55-inch one, and a 34-inch ultrawide 1% less tall than a 27-inch 16:9 monitor. The room step gave 59 to 80 inches for 8 feet and 73 to 99 inches for 3 meters. Empty, zero and negative input show a prompt instead of a result. Testing caught one problem we fixed: a 4K resolution could stay selected for an ultrawide screen and give a wrong PPI, so the resolution and the aspect ratio now follow each other.
Frequently asked questions
How is screen size measured?
Diagonally, from one corner of the visible picture to the opposite corner, without the frame (bezel). A 65-inch TV has a 65-inch diagonal picture; the width and height depend on its aspect ratio.
How wide is a 65 inch TV?
A 65-inch 16:9 TV has a picture about 56.7 inches wide and 31.9 inches high (144 × 81 cm). The whole TV is slightly larger because of the frame, so check the maker's spec sheet before you buy a stand or cabinet.
What size TV should I get for my room?
Measure from your seat to the screen. The SMPTE guideline (a 30° viewing angle) and the THX guideline (about 40°) give a range: from 8 feet away that is roughly a 59 to 80 inch 16:9 TV, and from 10 feet roughly 74 to 100 inches. Pick the lower end if you mostly watch TV shows, the upper end for films and games.
Is a 34 inch ultrawide bigger than a 27 inch monitor?
It is much wider but not taller. A 34-inch ultrawide (3440 × 1440) is about 31.4 × 13.1 inches, while a 27-inch 16:9 monitor is 23.5 × 13.2 inches, so the height is almost the same.
What is a good PPI for a monitor?
About 90 to 110 PPI looks sharp at normal desk distance without scaling, for example 24 inches at 1920 × 1080 (92 PPI) or 27 inches at 2560 × 1440 (109 PPI). 27 inches at 4K is 163 PPI, which looks very crisp but usually needs 150% scaling.
Can I measure my screen size with this page?
No. A browser can read your resolution but not the physical size of the screen. Measure the diagonal with a tape measure, or look up the model, then enter it here. To see your resolution, use the screen resolution checker.