TV and monitor sizes are quoted in inches in many countries, including many outside the US. A “55-inch TV” is also sold as a 55-inch model in many other regions — 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 calculated width and height (based on the nominal diagonal), 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 (55 × 2.54, using the nominal size). The advertised size is a rounded “class”, so the real panel can be slightly smaller: a 55-inch-class TV may measure about 54.6 inches.
The width and height depend on the aspect ratio. Most TVs and many 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 calculated dimensions of the picture area, based on the nominal diagonal, rounded to 0.1 in and 0.1 cm. Real panels can be a little smaller. 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
One retailer guideline (Crutchfield) for a 4K TV is to sit about 1 to 1.5 times the screen diagonal away. For a 55″ TV that is roughly 55–82.5 inches, or about 1.4 to 2.1 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. Check that your desk is wide and deep enough: the screen alone is about 70.8 cm wide before the frame and stand.
Related: Metric vs imperial explained · Paper sizes in inches and mm · CM to inches converter
Sources and Checking
- NIST Guide to the SI, Appendix B.8 (1 inch = 0.0254 m exactly)
- Width and height calculated for a 16:9 screen from the diagonal (width = diagonal × 16/√337, height = diagonal × 9/√337). Actual panels vary slightly by model.
Published by Johnson, who runs mmintoinches.com. Every value in this guide was recalculated from 1 inch = 25.4 mm and checked against the sources below on 9 October 2026. Found a mistake? Email support@mmintoinches.com with the page and the value.