TV Screen Size Calculator
A television's headline size is its diagonal, but what you really want to know when planning a wall or cabinet is the width and height. This calculator turns a diagonal measurement and an aspect ratio into the screen's width, height, and area, shown in both inches and centimetres. The maths is pure geometry: the diagonal, width, and height form a right triangle, so the sides follow from the aspect ratio and the Pythagorean relationship. The figures cover the active display area; add a margin for the bezel and stand.
Screen size formula
Let r = sqrt(aspect width^2 + aspect height^2)
Width = diagonal * aspect width / r
Height = diagonal * aspect height / r
Width in cm = width inches * 2.54
Area = width * height (square inches)
This comes straight from the Pythagorean theorem applied to the screen rectangle. The factor 2.54 is the exact inch-to-centimetre conversion. No empirical constant is assumed.
Screen size facts
- The diagonal is always longer than either the width or the height.
- Almost all modern TVs use a 16:9 aspect ratio.
- A 50-inch 16:9 screen is about 43.6 inches wide and 24.5 inches tall.
- Wider aspect ratios are shorter in height for the same diagonal.
- Add a margin for the bezel and stand when planning a fit.
TV screen size: frequently asked questions
How do you find TV width and height from the diagonal?
A screen's diagonal, width, and height form a right triangle. For an aspect ratio of width to height of a to b, the width equals the diagonal times a divided by the square root of a squared plus b squared, and the height equals the diagonal times b divided by the same square root.
What is the aspect ratio of most TVs?
Modern televisions are almost all 16:9, meaning 16 units of width for every 9 of height. Cinema content and some ultrawide monitors use 21:9. Enter whichever ratio matches your screen; the calculator uses the two numbers you provide.
Why is a 50-inch TV not 50 inches wide?
The 50 inches is the diagonal, the longest measurement corner to corner. For a 16:9 screen the width is about 43.6 inches and the height about 24.5 inches. The diagonal always exceeds either side, which is why the headline number sounds larger than the screen looks.
How is the screen area calculated?
Area is width multiplied by height. The calculator reports it in square inches and square centimetres. Two screens with the same diagonal but different aspect ratios have different areas; wider ratios are shorter and narrower ratios are taller for the same diagonal.
Does this account for the bezel?
No. The figures describe the active display area defined by the diagonal you enter. The physical product is slightly larger because of the bezel and stand. Check the manufacturer's dimensions when planning a wall mount or cabinet fit.
Official sources
- National Institute of Standards and Technology: inch to centimetre conversion.
- Federal Communications Commission: Digital Television guidance.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.