PPI calculator

Enter the resolution in pixels and the screen diagonal to get the pixel density in PPI. The tool also gives the dot pitch, the aspect ratio and the real width and height of the screen. Handy for comparing monitors, choosing a phone or checking whether a display looks sharp at your distance.

Width (pixels)

Height (pixels)

Screen diagonal

Diagonal unit

Pixel density (PPI)91.79

Dot pitch: 0.2767 mm
Aspect ratio: 16:9
Screen width: 20.92 in (53.1 cm)
Screen height: 11.77 in (29.9 cm)
Total pixels: 2.07 MP

Runs in your browser: nothing you enter is sent anywhere.

How to use it

Type the resolution in pixels, for example 2560 and 1440.
Enter the diagonal and choose inches, centimetres or millimetres.
Read the PPI, the dot pitch and the real size of the screen.

Formulas

Result	Formula
PPI	√(w² + h²) ÷ diagonal (in)
Dot pitch	25.4 mm ÷ PPI
Width (in)	w ÷ PPI
Height (in)	h ÷ PPI

Worked example

A 3840 × 2160 monitor with a 27 inch diagonal has a pixel diagonal of √(3840² + 2160²) = 4406.4. PPI is 4406.4 ÷ 27 = 163.2 and the dot pitch is 25.4 ÷ 163.2 = 0.156 mm. The width is 3840 ÷ 163.2 = 23.5 inches.

Notes

The aspect ratio is reduced to lowest terms. Some resolutions such as 1366 × 768 do not reduce neatly, so the nearest common ratio is named as well.
Use the diagonal of the visible image, not of the case.

Frequently asked questions

How is PPI calculated?

PPI = √(width² + height²) ÷ diagonal in inches. The square root is the diagonal measured in pixels. A 1920 × 1080 screen has a pixel diagonal of 2202.9, so at 24 inches it has 2202.9 ÷ 24 = 91.8 PPI.

What is dot pitch?

Dot pitch is the distance between the centres of two neighbouring pixels. It is 25.4 mm divided by the PPI, so 91.8 PPI gives 0.277 mm. A smaller dot pitch means finer detail.

What PPI counts as sharp?

It depends on viewing distance. A desktop monitor viewed at arm's length looks good from roughly 110 PPI upwards, and phones held close usually have 300 to 500 PPI. The calculator gives the number; the distance decides what you notice.

Is PPI the same as DPI?

PPI counts pixels on a screen and DPI counts printed dots per inch. People often mix them up, and the arithmetic is the same: the number of units along one inch.

Why does my phone's advertised PPI differ from the result?

The advertised diagonal is usually rounded, and rounded corners or notches change what is measured. Small differences of a few PPI are normal.

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