Screens are one of the few things measured in inches almost everywhere in the world. A “55-inch TV” is sold as 55 inches in Europe, Asia and Africa too — sometimes with the centimeter size in small print. But the number only tells you the diagonal, not how wide or tall the screen is. This guide converts common TV and monitor sizes to centimeters and gives the real width and height, so you can check whether a screen will fit your wall, cabinet or desk.
Screen Size Is the Diagonal
A screen’s size is measured corner to corner across the visible picture area, not including the frame (bezel). To convert the diagonal: inches × 2.54 = centimeters. A 55″ TV has a 139.7 cm diagonal.
The width and height depend on the aspect ratio. Almost all TVs and most monitors are 16:9, meaning 16 units wide for every 9 units tall.
TV and Monitor Sizes: 16:9 Screens
| Screen size | Diagonal (cm) | Width × height (in) | Width × height (cm) |
|---|---|---|---|
| 24″ | 61.0 cm | 20.9 × 11.8 in | 53.1 × 29.9 cm |
| 27″ | 68.6 cm | 23.5 × 13.2 in | 59.8 × 33.6 cm |
| 32″ | 81.3 cm | 27.9 × 15.7 in | 70.8 × 39.8 cm |
| 40″ | 101.6 cm | 34.9 × 19.6 in | 88.6 × 49.8 cm |
| 43″ | 109.2 cm | 37.5 × 21.1 in | 95.2 × 53.5 cm |
| 50″ | 127.0 cm | 43.6 × 24.5 in | 110.7 × 62.3 cm |
| 55″ | 139.7 cm | 47.9 × 27.0 in | 121.8 × 68.5 cm |
| 65″ | 165.1 cm | 56.7 × 31.9 in | 143.9 × 80.9 cm |
| 75″ | 190.5 cm | 65.4 × 36.8 in | 166.0 × 93.4 cm |
| 85″ | 215.9 cm | 74.1 × 41.7 in | 188.2 × 105.8 cm |
These are the dimensions of the picture area. The TV itself is slightly larger because of the frame and stand — check the manufacturer’s specification sheet for exact outside dimensions before buying a cabinet or wall bracket.
How to Work Out Width and Height Yourself
For a 16:9 screen with diagonal d:
- Width ≈ d × 0.872
- Height ≈ d × 0.490
Example: a 65″ TV is about 65 × 0.872 = 56.7″ wide (144 cm) and 65 × 0.490 = 31.9″ tall (81 cm).
These factors come from the Pythagorean theorem: the diagonal of a 16 × 9 rectangle is √(16² + 9²) ≈ 18.36, so width = 16 ÷ 18.36 and height = 9 ÷ 18.36 of the diagonal.
Ultrawide Monitors (21:9)
Ultrawide monitors are much wider and shorter than a 16:9 screen with the same diagonal. A 34″ ultrawide (about 3440 × 1440 pixels) is roughly 31.4″ × 13.1″ (80 × 33 cm) — about as tall as a 27″ 16:9 monitor but far wider. Always compare width and height, not just the diagonal, when switching between aspect ratios.
Phones and Tablets
Phone and tablet screens are also quoted as diagonals in inches: a 6.1″ phone screen is 15.5 cm across the diagonal, and an 11″ tablet is 27.9 cm. Because phones use tall aspect ratios with rounded corners, two phones with the same diagonal can have noticeably different widths.
Choosing a Size for Your Room
A common guideline is to sit about 1.2 to 1.6 times the screen diagonal away for a 4K TV. For a 55″ TV that is roughly 66–88 inches, or about 1.7 to 2.2 meters. Treat this as a starting point — personal preference and the room layout matter more than any formula.
Frequently Asked Questions
How many cm is a 55 inch TV?
The diagonal is 139.7 cm. The picture area is about 121.8 cm wide and 68.5 cm tall.
How wide is a 65 inch TV?
About 56.7 inches (144 cm) for the screen area, plus the frame.
Is a 32 inch monitor too big for a desk?
A 32″ 16:9 monitor is about 27.9″ (70.8 cm) wide. It suits a desk at least 120 cm wide and a viewing distance of around 70–90 cm.
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