When you need this tool
Checking whether a monitor fits a desk or a shelf, whether a TV fits a wall space, or how two screens compare. Diagonal size alone is misleading: a 34-inch ultrawide is about as tall as a 27-inch 16:9 monitor.
How it’s calculated
The aspect ratio forms a right triangle with its own diagonal: for 16:9 that’s √(16² + 9²) = 18.358. The real width is the screen diagonal × 16 ÷ 18.358, and the height is the diagonal × 9 ÷ 18.358.
Comparing screens
- Height matters for documents and code. A 27-inch 16:9 screen is about 13.2 in tall; a 32-inch 16:9 is about 15.7 in.
- Area matters for movies and games. Area grows with the square of the diagonal, so a 65-inch TV has about 40% more screen than a 55-inch.
- Ultrawides trade height for width. A 34-inch 21:9 monitor is about as tall as a 27-inch 16:9, but 7.8 inches wider.
Common mistakes
Comparing diagonals across aspect ratios. A 13-inch 3:2 laptop screen has more area than a 13-inch 16:9 one.
Forgetting the stand. Monitor stands add height; check the full product dimensions.
For pixel density, use the screen PPI calculator.