📺 Displays
TV & Monitor Size Calculator
Work out the physical width, height and pixel density of a TV or monitor from its diagonal and aspect ratio. Press Calculate.
About the TV & Monitor Size Calculator
A screen's diagonal is measured corner to corner, not across the width. For a 16:9 display, width = diagonal × 16 ÷ √(16² + 9²) and height = diagonal × 9 ÷ √(16² + 9²). A 55-inch 16:9 TV is about 121.8 cm wide and 68.5 cm tall.
Pixel density uses the native resolution and the diagonal in inches: PPI = √(width² + height²) ÷ diagonal. A 55-inch 4K TV is about 80 PPI; a 27-inch 1440p monitor is about 109 PPI. Viewing distance matters more than PPI for perceived sharpness on a TV.
How the calculation works
- Width = diagonal × w ÷ √(w² + h²).
- Height = diagonal × h ÷ √(w² + h²).
- Area = width × height.
- PPI = √(pixel width² + pixel height²) ÷ diagonal inches.
Reference values
| Diagonal | 16:9 width | 16:9 height | 4K PPI |
|---|---|---|---|
| 24 in | 53.1 cm | 29.9 cm | 183 |
| 27 in | 59.8 cm | 33.6 cm | 163 |
| 32 in | 70.8 cm | 39.8 cm | 138 |
| 55 in | 121.8 cm | 68.5 cm | 80 |
| 65 in | 143.9 cm | 80.9 cm | 68 |
| 75 in | 166.0 cm | 93.4 cm | 59 |
Worked example: a 65-inch TV and a 34-inch ultrawide
A 65-inch 16:9 TV is 143.9 cm wide and 80.9 cm tall. Check the stand and wall space for that width, not just the diagonal. A 34-inch 21:9 monitor is 79.4 cm wide and 34.0 cm tall—narrower than a 40-inch 16:9 TV but much wider than a 27-inch 16:9 monitor.
At 4K, the 65-inch TV is about 68 PPI. From eight feet away that is comfortably sharp; from three feet it is not a monitor substitute. The 34-inch 3440 × 1440 ultrawide is about 110 PPI, which is a comfortable desktop density without scaling.
Viewing distance and field of view
The comfortable viewing distance for a television depends on resolution as well as size. A common guide for 4K is about 1.5 times the screen height, or roughly 1.2 m for a 55-inch set; for 1080p it is closer to 3 times the height. Sitting closer than that makes individual pixels visible without adding perceived detail, while sitting much further away wastes the extra resolution.
Cinema-style viewing puts the screen at about 30–40° of horizontal field of view, which for a 65-inch 16:9 TV is roughly 2.0–2.7 m. Desktop monitors are used far closer, which is why a 27-inch 1440p panel at 60 cm looks sharp at 109 PPI while the same density on a television would look soft from across a room.