Screen Size Calculator (TV inches to cm)
Width, height, area, PPI and viewing distance from a screen’s diagonal and aspect ratio.
TV and monitor sizes are the diagonal of the picture, e.g. 55 or 139.7 cm.
47.9 × 27.0 in · 8,339 cm² · 80.1 PPI at 3840 × 2160
| Measure | Metric | Imperial |
|---|---|---|
| Width | 121.8 cm | 47.9 in |
| Height | 68.5 cm | 27.0 in |
| Diagonal | 139.7 cm | 55.0 in |
| Viewable area | 8,339 cm² | 1,293 in² |
| Pixel density | 31.5 px per cm | 80.1 PPI |
| Pixel pitch | 0.3171 mm | 0.01248 in |
| Pixels | 3840 × 2160 | 8.29 megapixels |
Viewing distance
Reference only: how far away the screen fills a given part of your view. Closer is more immersive; further is more relaxed.
| Guideline | Distance |
|---|---|
| THX: 40° of your view (closest recommended) | 1.67 m (5 ft 6 in) |
| SMPTE: 30° of your view | 2.27 m (7 ft 5 in) |
| Your angle: 36° | 1.87 m (6 ft 2 in) |
| Single pixels stop being visible (1 arc-minute, 20/20 vision) | beyond 1.09 m (3 ft 7 in) |
Compare with another screen
Find the right size for a wall or a sofa
Uses the aspect ratio chosen above. TV cases are a little larger than the picture, so leave some room around it.
About the Screen Size Calculator (TV inches to cm)
A TV or monitor size is the diagonal of the picture, so a 55-inch 16:9 TV and a 55-inch 4:3 one are not the same width. Type the diagonal in inches or centimetres and choose the aspect ratio — 16:9, 16:10, 21:9, 32:9, 4:3, 3:2, a custom ratio or the one implied by a resolution — to get the width, height and viewable area in both units.
Add a resolution to see the pixel density (PPI) and pixel pitch, and read off a viewing-distance range from the THX 40° and SMPTE 30° field-of-view guidelines and the distance at which single pixels stop being visible. Compare two screens by area, or work back from the width of a wall or the distance to your sofa.
How to use it
- Type the diagonal (for example
55,55"or139.7 cm) and pick inches or cm. - Choose the aspect ratio. For ultrawide monitors pick the exact one (64:27 for 2560 × 1080, 43:18 for 3440 × 1440) or From the resolution below.
- Optionally choose the resolution to get the PPI, pixel pitch and the distance at which pixels blend.
- Read the width, height and area, and the viewing distances; type your own viewing angle if you prefer another.
- Open Compare with another screen or Find the right size for a wall or a sofa for the reverse questions.
Examples
55 in, 16:9, 3840 × 2160
121.8 × 68.5 cm (47.9 × 27.0 in) · 80.1 PPI · viewing distance 1.67 m (THX 40°) to 2.27 m (SMPTE 30°)
65 in, 16:9
143.9 × 80.9 cm (56.7 × 31.9 in), 39.7% more area than a 55-inch
27 in, 16:9, 2560 × 1440
59.8 × 33.6 cm · 108.8 PPI
34 in, 3440 × 1440 (43:18)
79.7 × 33.3 cm · 109.7 PPI
150 cm, 16:9
Up to a 67.8-inch picture (a 65-inch TV, allowing for the case)
Common uses
- Checking whether a new TV fits a wall, a cabinet or an alcove before buying.
- Comparing a 55-inch with a 65-inch, or a 27-inch 16:9 monitor with a 34-inch ultrawide.
- Working out the pixel density of a monitor or a laptop screen from its size and resolution.
- Choosing a screen size for the distance from your sofa or desk.
The formulas
For a diagonal d and an aspect ratio w:h:
- width = d × w ÷ √(w² + h²) and height = d × h ÷ √(w² + h²) — for 16:9, width = 0.8716 × d and height = 0.4903 × d
- area = width × height
- PPI = √(pixels across² + pixels down²) ÷ diagonal in inches; pixel pitch = 25.4 mm ÷ PPI
- viewing distance for a horizontal viewing angle θ = (width ÷ 2) ÷ tan(θ ÷ 2)
One inch is exactly 2.54 cm, so a 55-inch diagonal is 139.7 cm.
Viewing distance guidelines
THX recommends a seat where the screen fills about 40° of your horizontal view for the best cinema-like experience; for a 16:9 screen that is about 1.2 × the diagonal (1.67 m for a 55-inch). The 30° figure usually quoted from SMPTE’s EG 18 guideline gives about 1.6 × the diagonal (2.27 m for a 55-inch). These are reference points for immersion, not rules: sit further back if you prefer.
With a resolution, the calculator also gives the distance beyond which one pixel spans less than one arc-minute — the detail a person with 20/20 (6/6) vision can just make out. Beyond it, extra resolution is hard to see.
Aspect ratios and “21:9”
Screens sold as 21:9 are not exactly that: a 2560 × 1080 monitor is 64:27 (2.37:1) and a 3440 × 1440 one 43:18 (2.39:1). The difference changes the width by about 1–2%, so pick the exact ratio or From the resolution below when it matters. If the resolution you choose does not match the ratio, the calculator warns you.
Limitations
- The size is the picture’s diagonal; the case (bezel and stand) is larger — check the maker’s specifications for the full dimensions.
- Some TVs are sold as a size “class” rounded from the viewable diagonal; use the viewable size from the specifications for exact results.
- Viewing-distance guidelines assume a centred seat and the whole picture in view; they are not health advice.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How wide is a 55-inch TV?
A 55-inch 16:9 TV’s picture is 121.8 cm wide and 68.5 cm tall (47.9 × 27.0 in). The case adds a little.
How do I convert TV inches to cm?
Multiply by 2.54: a 55-inch diagonal is 139.7 cm. The width and height depend on the aspect ratio — this calculator works them out.
How far should I sit from a 65-inch TV?
About 1.98 m for THX’s 40° and 2.69 m for the 30° SMPTE figure. With 4K, single pixels become invisible beyond about 1.29 m.
How much bigger is a 65-inch TV than a 55-inch?
With the same aspect ratio, area grows with the square of the diagonal: (65 ÷ 55)² = 1.397, so 39.7% more picture.
What is PPI?
Pixels per inch: how densely a screen packs its pixels. A 27-inch 2560 × 1440 monitor has 108.8 PPI; a 55-inch 4K TV 80.1 PPI.