Screen Dimensions from Diagonal Calculator
Screens are advertised by their diagonal, but to fit one in a space or compare picture area you need the actual width and height. Those come straight from the diagonal and the aspect ratio using the Pythagorean theorem. Enter the diagonal size in inches and the aspect ratio as two numbers (for example 16 and 9), and this calculator returns the width, the height, the screen area in square inches, and the same area in square centimeters. The geometry is exact: the diagonal is the hypotenuse of the width and height.
Screen dimensions formula
r = sqrt(aspect width^2 + aspect height^2)
Width = diagonal * aspect width / r
Height = diagonal * aspect height / r
Area (sq in) = width * height
Area (sq cm) = area sq in * 6.4516 (since 1 inch = 2.54 cm)
The diagonal is the hypotenuse, so scaling the aspect-ratio rectangle to that diagonal gives the true width and height.
Screen geometry context
- For 16:9, width is about 87.2 percent of the diagonal and height about 49.0 percent.
- A 50-inch 16:9 screen is roughly 43.6 by 24.5 inches.
- For the same diagonal, a 4:3 screen has more area than a 16:9 screen.
- Ultrawide 21:9 screens are wider but shorter than 16:9 at the same diagonal.
- One inch equals exactly 2.54 centimeters, so one square inch is 6.4516 square centimeters.
Screen dimensions calculator: frequently asked questions
How do I find screen width and height from the diagonal?
Use the aspect ratio with the Pythagorean theorem. For a ratio of w to h, the diagonal d gives width = d times w divided by the square root of (w squared plus h squared), and height = d times h divided by that same square root. A 50-inch 16:9 TV is about 43.6 inches wide and 24.5 inches tall.
Why is a 50-inch TV not 50 inches wide?
Because the advertised size is the diagonal, not the width. For a 16:9 screen the width is roughly 87 percent of the diagonal and the height roughly 49 percent. The diagonal is always the longest measurement across the rectangle.
What is the area of a screen?
Multiply the calculated width by the calculated height. A 50-inch 16:9 screen is about 43.6 by 24.5 inches, giving roughly 1,068 square inches. This is useful for comparing how much picture two differently shaped screens actually show.
How do aspect ratios compare in usable area?
For the same diagonal, a squarer ratio like 4:3 has more area than a wider ratio like 21:9, because the wide screen stretches the diagonal across a thinner rectangle. That is why two TVs with the same advertised size can differ in picture area.
What aspect ratios should I enter?
Enter the ratio your screen uses: 16:9 for most TVs and monitors, 16:10 for some laptops, 21:9 for ultrawide displays, or 4:3 for older screens. Enter the two numbers separately so the tool can apply the geometry exactly.
Official sources
- NIST: Unit conversion, inches to centimeters (2.54 cm per inch).
- Video Electronics Standards Association: VESA display standards.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.