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Technologydesign

Screen Size Calculator

Actual width, height and area from a screen diagonal. Two screens with the same diagonal in different aspect ratios have noticeably different areas, which is what the diagonal convention hides.

Also called: monitor size calculator, tv dimensions, ppi calculator.

Width (inches)
23.53

A 27 inch 16:9 screen is 23.53 wide and 13.24 tall, an area of 311.5 square inches. At 109 pixels per inch, text is comfortable at normal distance.

Height (inches)
13.24
Area (square inches)
311.5
Width (cm)
59.77
Pixels per inch
108.8
On pixel density
At 109 pixels per inch, text is comfortable at normal distance.
How this is calculated
Method and background

How this is calculated

The diagonal and the aspect ratio determine the sides by Pythagoras. The consequence worth knowing is that area is not proportional to the diagonal across aspect ratios: a 27 inch 16:9 panel has less area than a 27 inch 16:10 one, and considerably less than a 27 inch 4:3. Pixel density follows from the horizontal resolution and the computed width, and is what actually determines how sharp text looks.

the diagonal splits into width and height by the aspect ratio
d
Diagonal (inches)
r_w : r_h
Aspect ratio

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

a 27 inch 16:9 monitor

Diagonal (inches)
27
Aspect ratio width
16
Aspect ratio height
9
Horizontal resolution
2,560

Width (inches)23.53

Computed independently from the diagonal and ratio

Open this example

a square screen is wider for the same diagonal

Diagonal (inches)
27
Aspect ratio width
1
Aspect ratio height
1
Horizontal resolution
0

Width (inches)19.09

boundary: the largest area for a given diagonal

Open this example

Method and limits

What it assumes

  • The diagonal is the panel diagonal rather than the bezel.

What it deliberately does not model

  • Curved screens measure along the curve, which overstates the flat width slightly.

Formula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator

Frequently asked questions

Is a 27 inch monitor always the same size?
No. Only if the aspect ratio matches. A 27 inch ultrawide is much wider and shorter than a 27 inch 16:9, with a different area.
What pixel density is good?
Around 110 pixels per inch is the traditional desktop standard and text is visibly pixelated below about 90. Above roughly 180 the eye stops resolving individual pixels at normal viewing distance.