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A screen’s inch rating measures the diagonal, not the width. One inch is 2.54 cm, so a 27-inch monitor has a 68.6 cm diagonal, and a 16:9 screen of that size is 59.8 cm (23.5 in) wide and 33.6 cm (13.2 in) tall. A 55-inch 16:9 TV screen is about 47.9 in (121.8 cm) wide and 27.0 in (68.5 cm) tall.
The most common misunderstanding when buying a monitor or TV is to read “27 inches” as the width. The inch figure only tells you how long the diagonal is; you need the aspect ratio to work out the width and height. The common sizes are all worked out below.
16:9 monitor and TV size chart
| Size | Diagonal (cm) | Width (in) | Height (in) | Width (cm) | Height (cm) | Typical use |
|---|---|---|---|---|---|---|
| 13 in | 33 | 11.3 | 6.4 | 28.8 | 16.2 | Small laptops |
| 14 in | 35.6 | 12.2 | 6.9 | 31 | 17.4 | Laptops |
| 15.6 in | 39.6 | 13.6 | 7.6 | 34.5 | 19.4 | Laptops |
| 21.5 in | 54.6 | 18.7 | 10.5 | 47.6 | 26.8 | Desktop monitors |
| 24 in | 61 | 20.9 | 11.8 | 53.1 | 29.9 | Desktop monitors |
| 27 in | 68.6 | 23.5 | 13.2 | 59.8 | 33.6 | Desktop monitors |
| 32 in | 81.3 | 27.9 | 15.7 | 70.8 | 39.8 | Large monitors, small TVs |
| 43 in | 109.2 | 37.5 | 21.1 | 95.2 | 53.5 | TVs |
| 50 in | 127 | 43.6 | 24.5 | 110.7 | 62.3 | TVs |
| 55 in | 139.7 | 47.9 | 27.0 | 121.8 | 68.5 | TVs |
| 65 in | 165.1 | 56.7 | 31.9 | 143.9 | 80.9 | TVs |
| 75 in | 190.5 | 65.4 | 36.8 | 166 | 93.4 | TVs |
(Figures are for the visible screen area and do not include the bezel.)
The widths and heights in the table stop at the edge of the picture. In real life you have to add the bezel, and for a TV the stand as well, so leave at least a few extra centimeters (an inch or two) when measuring a TV stand or a wall.
Work it out yourself: multiply by the ratio factor
- For the diagonal in centimeters, multiply the inch size by 2.54.
- For a 16:9 screen: width = diagonal × 0.872, height = diagonal × 0.49.
- For a 16:10 screen: width = diagonal × 0.848, height = diagonal × 0.53.
The factors work the same whether the diagonal is in inches or centimeters. They come from the Pythagorean theorem: the diagonal of a 16:9 rectangle is √(16² + 9²) ≈ 18.36 units, so the width is 16 ÷ 18.36 ≈ 0.872 of the diagonal and the height is 9 ÷ 18.36 ≈ 0.49. At the same inch size, a flatter screen is wider and shorter, so a 34-inch 21:9 ultrawide monitor is actually about as tall as a 27-inch 16:9 monitor. For how the ratios differ, see 16:9 Aspect Ratio.
16:10, common on laptops
In recent years, many laptops have switched to 16:10, which is a little taller than 16:9 and shows a line or two more:
| Size (16:10) | Width (in) | Height (in) | Width (cm) | Height (cm) |
|---|---|---|---|---|
| 13.3 in | 11.3 | 7.0 | 28.6 | 17.9 |
| 14 in | 11.9 | 7.4 | 30.2 | 18.8 |
| 16 in | 13.6 | 8.5 | 34.5 | 21.5 |
At 14 inches, a 16:10 screen is about 0.8 cm narrower and about 1.4 cm taller than a 16:9 one. The laptop body is larger still once you add the bezel and keyboard deck, so when buying a bag or sleeve, go by the body dimensions the manufacturer publishes.
The same word “inch,” three different measurements
| Item | What the “inch” measures | Example |
|---|---|---|
| Monitors and TVs | The diagonal | 27-inch monitor = 68.6 cm diagonal |
| Photo prints | The side lengths in inches | A 4 × 6 print is 4 in × 6 in (10.16 × 15.24 cm); in Chinese it is called a “6-inch photo” after its long side |
| ID photos in Taiwan | A photo-studio trade name, unrelated to inches | A “2-inch” photo = 3.5 × 4.5 cm |
All three use the same word, but they are measured in completely different ways. For how photo sizes are named, see How Big Is a 4×6 Photo in Centimeters? and the Paper and Photo Size Chart; for the ID photo naming, see How Big Is a Taiwanese 2-Inch ID Photo?
Frequently asked questions
Where is a screen’s inch size measured?
Along the diagonal of the screen, from the bottom-left corner to the top-right corner. That is why a 27-inch 16:9 monitor and a 27-inch 21:9 monitor have different widths and heights; you need the aspect ratio to work out the width and height.
How big is a 27-inch monitor in centimeters?
Its diagonal is 68.6 cm. On a 16:9 monitor, the screen is 59.8 cm (23.5 in) wide and 33.6 cm (13.2 in) tall, with the bezel on top of that.
What are the dimensions of a 55-inch TV?
A 16:9 55-inch TV has a screen about 121.8 cm (47.9 in) wide and about 68.5 cm (27.0 in) tall, with a 139.7 cm diagonal. When measuring a TV stand or a wall, add the width of the bezel and the stand.
How many centimeters is an inch?
One inch is 2.54 cm. Multiply a screen’s inch size by 2.54 to get its diagonal in centimeters; for example, 24 inches is 61 cm.
Keywords: 55 inch TV dimensions, TV size dimensions, TV sizes in inches and cm, monitor size, 27 inch monitor dimensions, screen size diagonal, 65 inch TV dimensions, laptop screen size, inches to cm, 16:10
Sources: Chinese original first published 2026-10-09. Widths and heights are calculated for the visible screen area only and do not include the bezel or stand. Inch figures are converted from the Chinese original's centimeter values.
This English version is based on original Traditional Chinese content on joelin.cc. The language and explanations are localised for international readers. The Traditional Chinese original is the authoritative version — for its complete meaning, please read the original article.