Screen Size Calculator
A diagonal alone does not tell you how big a screen is.
The diagonal hides the shape
Screens are sold by diagonal, which conceals the thing you usually want to know: how much space it takes on a wall, and how much picture you get.
Two screens with the same diagonal can differ substantially in area. A 34-inch 21:9 ultrawide has noticeably less screen area than a 34-inch 16:9 panel would, because a more elongated rectangle with the same diagonal encloses less.
width = diagonal × ratio₁ ÷ √(ratio₁² + ratio₂²)
Area grows with the square of the diagonal
This is what makes television upgrades misleading. Going from 55 to 65 inches sounds like an 18 % increase; the area increase is 40 %. From 43 to 65 inches is well over double.
The table above shows area as a percentage of a 32-inch screen, which is a more useful comparison than the diagonal.
Measuring for a space
The screen dimensions above are the panel. A television or monitor also has a bezel, and a stand that is usually wider than the screen. Add 2–5 cm on each side and check the stand's footprint separately — a common and expensive mistake is buying a television whose feet are wider than the unit it sits on.
For wall mounting, the VESA pattern matters more than the size, and it is quoted separately.
What size to buy
The usual guidance works from viewing distance rather than room size. For a television at three metres, most people are comfortable somewhere between 55 and 75 inches, depending on how immersive they want it. The viewing distance calculator works it out from the recommendations.
Almost nobody reports regretting a larger television. Plenty report the opposite.
Common uses
- Checking a screen fits a space or a piece of furniture.
- Comparing two sizes by area rather than diagonal.
- Working out a wall mount position.
- Comparing an ultrawide against a standard monitor.
Questions people ask
How do I find a screen's width from its diagonal?
Multiply the diagonal by the ratio width and divide by √(w² + h²). A 55-inch 16:9 screen is about 48 inches wide.
How much bigger is a 65-inch screen than a 55-inch?
About 40 % more area, though the diagonal is only 18 % larger. Area grows with the square.
Do ultrawide monitors have less screen than standard ones?
At the same diagonal, yes. A more elongated rectangle encloses less area for the same diagonal.
How much space should I allow beyond the screen?
Two to five centimetres each side for the bezel, and check the stand's footprint separately — feet are often wider than the furniture they sit on.
Nothing is sent anywhere
The arithmetic runs in the page. Where a tool reads your screen dimensions, it reads what the browser already exposes to every site you visit — and it does not transmit them. The about page lists every request this site makes.