Frame Rate Test

Screen Size Calculator

Work out the real width, height, and area of any screen from its aspect ratio and a single measurement — a TV, monitor, projector, and computer screen size calculator in one. Enter a diagonal, width, or height and get the rest in both inches and centimetres.

1. Choose aspect ratio

Custom:

2. Enter a measurement

I know the…

TVs and monitors are advertised by their diagonal. Switch to width or height to check whether a screen fits a shelf or wall.

Dimensions

Diagonal (entered)
55"
139.7 cm
Width
47.9"
121.8 cm
Height
27"
68.5 cm
Screen area
1,293 in²
8,339 cm²
Aspect ratio
16:9
1.78 : 1

Shape preview (16:9)

47.9" · 121.8 cm
55" diagonal
27" · 68.5 cm

Common 16:9 screen sizes

A screen dimensions chart of the width, height, and area for standard diagonal sizes at the selected aspect ratio.

DiagonalWidthHeightArea
13.3"11.6" · 29.4 cm6.5" · 16.6 cm76 in²
15.6"13.6" · 34.5 cm7.6" · 19.4 cm104 in²
21.5"18.7" · 47.6 cm10.5" · 26.8 cm198 in²
24"20.9" · 53.1 cm11.8" · 29.9 cm246 in²
27"23.5" · 59.8 cm13.2" · 33.6 cm312 in²
32"27.9" · 70.8 cm15.7" · 39.8 cm438 in²
40"34.9" · 88.6 cm19.6" · 49.8 cm684 in²
43"37.5" · 95.2 cm21.1" · 53.5 cm790 in²
50"43.6" · 110.7 cm24.5" · 62.3 cm1,068 in²
55"47.9" · 121.8 cm27" · 68.5 cm1,293 in²
65"56.7" · 143.9 cm31.9" · 80.9 cm1,805 in²
75"65.4" · 166 cm36.8" · 93.4 cm2,404 in²
85"74.1" · 188.2 cm41.7" · 105.8 cm3,087 in²
Retina Display Calculator

Add a resolution to get pixel density (PPI), the retina viewing distance, and dot pitch.

What Is My Screen Size?

Detect your current screen's resolution, viewport, and pixel ratio automatically.

How the Screen Size Calculator Works

A screen's diagonal alone does not tell you how wide or tall it is — that depends on the screen ratio. Acting as a screen ratio calculator and aspect ratio calculator, this screen size calculator (also a TV size calculator, monitor size calculator, and 16:9 calculator) fixes the proportion, then uses the one measurement you already know to solve the whole rectangle. Enter a diagonal to find the width and height, or enter a width or height to find the diagonal that fits — it will calculate the monitor dimensions instantly in centimetres and inches.

How to Measure Screen Size

1. Measure the diagonal

Run a tape measure corner to corner across the visible panel only, skipping the bezel. That distance is the screen size manufacturers advertise.

2. Pick the aspect ratio

Choose 16:9 for most TVs and monitors, 16:10 or 3:2 for many laptops, 21:9 for ultrawides, or 4:3 for classic and tablet displays.

3. Read width & height

The calculator returns the exact width, height, and area in both inches and centimetres — handy before buying, mounting, or fitting a screen into furniture.

The Formulas

Diagonal factor
k = √(w² + h²)
From the diagonal
width = D·w ÷ k · height = D·h ÷ k
From the width
height = W·h ÷ w · diagonal = W·k ÷ w

Frequently Asked Questions

For an aspect ratio of w:h, first find the diagonal factor k = √(w² + h²). The width is diagonal × w ÷ k and the height is diagonal × h ÷ k. For a 16:9 screen, k = √(16² + 9²) ≈ 18.36, so a 55-inch TV is 55 × 16 ÷ 18.36 ≈ 47.9 inches wide and 55 × 9 ÷ 18.36 ≈ 27.0 inches tall. This screen size calculator does the maths instantly in both inches and centimetres.
Screen size is the diagonal — measure in a straight line from one corner of the visible panel to the opposite corner, ignoring the bezel or frame. A tape measure across a 27-inch monitor should read about 27 inches (68.6 cm) corner to corner. Enter that diagonal above with the correct aspect ratio to get the exact width and height.
A 55-inch 16:9 screen is about 47.9 inches (121.8 cm) wide and 27.0 inches (68.5 cm) tall, with a viewing area of roughly 1293 in². Remember the 55 inches refers only to the diagonal of the panel — the physical cabinet is a little larger because of the bezel and stand.
Yes. Switch the "I know the…" selector to Width or Height and enter the measurement you have. This is ideal when you are checking whether a screen fits a TV stand, shelf, or recess — enter the available width and the calculator returns the largest matching diagonal and the height.
The aspect ratio is the proportion of width to height (16:9, 21:9, 4:3, and so on). Once you fix the ratio, a single known measurement determines the whole rectangle. Pick a preset such as 16:9 or type a custom ratio like 2.39:1, then enter any one dimension to solve the other two.
The advertised size is the diagonal, not the width. A 32-inch 16:9 monitor is only about 27.9 inches (70.9 cm) wide — narrower than the number suggests because the 32 inches runs corner to corner. Wider aspect ratios look even less tall: a 34-inch 21:9 ultrawide is about 31.3 inches wide but only 13.4 inches high.
One inch equals 2.54 centimetres, so multiply inches by 2.54 to get centimetres, or divide centimetres by 2.54 to get inches. A 24-inch screen is 60.96 cm on the diagonal. This calculator shows every dimension in both units at once, so you never have to convert by hand.
No. Screen size measures only the active display area, corner to corner. The full product is bigger once you add the bezel, frame, and stand, so always check the manufacturer's product dimensions — not just the diagonal — when planning whether a TV or monitor will physically fit.
This screen size calculator works purely from physical geometry — aspect ratio plus one measurement — and needs no pixel resolution. If you also want pixel density (PPI), dot pitch, or the retina viewing distance, add your resolution in the Retina Display Calculator, which is linked above.
Most TVs and modern monitors are 16:9. Many laptops use 16:10, ultrawide monitors are 21:9 or 32:9, older displays and iPads are 4:3, and Microsoft Surface devices are 3:2. If you know your resolution, divide width by height: 1920 ÷ 1080 = 1.78, which is 16:9. Use "What Is My Screen Size" to detect your resolution automatically.
Yes. Pick any proportion — 16:9, 16:10, 21:9, 4:3, or a custom ratio such as 2.39:1 — and it works as an aspect ratio calculator and screen ratio calculator, returning the matching width and height. For home cinema, enter your available width or desired diagonal and it doubles as a projector screen size calculator, giving the screen dimensions in both inches and centimetres.
Measure the LCD panel diagonally, corner to corner of the lit area only, leaving out the plastic bezel — that single number is the screen size. Enter it here as a computer screen size calculator, choose the aspect ratio (16:9 for most laptops and monitors, 16:10 or 3:2 for some), and it returns the exact display dimensions. This is the reliable way to measure LCD size without lining up a square.
For 16:9, the width is about 0.872 × the diagonal and the height is about 0.490 × the diagonal. So a 24-inch screen is roughly 20.9 × 11.8 inches (53.1 × 29.9 cm) and a 65-inch TV is about 56.7 × 31.9 inches (144 × 81 cm). The reference table above lists the 16:9 dimensions for every common size, and you can switch the ratio to get the dimensions for 21:9, 4:3, and more.

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