What This Calculator Finds
Manufacturers list a display’s size as a single diagonal measurement, such as 27 inches, but that alone doesn’t tell you the actual width and height. This calculator uses the diagonal size together with the screen’s aspect ratio (like 16:9 or 4:3) to work out the real width and height.
The Formula
Using the Pythagorean theorem, the height is calculated as Height = Diagonal / sqrt(ratio^2 + 1), where ratio is aspect width divided by aspect height. Width is then found as Width = Height x ratio. This works because the diagonal, width, and height form a right triangle.
Things to Note
- Common aspect ratios include 16:9 (widescreen), 16:10, 21:9 (ultrawide), and 4:3 (older monitors and TVs).
- Results are the visible screen dimensions only and don’t include the bezel or overall device size.
- Figures are approximate and intended for general reference and shopping comparisons.
Last reviewed August 2026