Screen PPI calculator

Pixel density and physical size of any screen from its resolution and diagonal.

Formula Screens & design

Pixel density

Rounded for display

Pixels per centimetre: ≈ 36.14 px/cm
Dot pitch: ≈ 0.2767 mm
Width: ≈ 53.13 cm
Height: ≈ 29.89 cm
Width in inches: ≈ 20.92 in
Height in inches: ≈ 11.77 in
Total pixels: ≈ 2.07 MP

How it works

The diagonal in pixels is found with Pythagoras’ theorem from the width and height in pixels. Dividing it by the diagonal in inches gives pixels per inch (PPI).

Dot pitch is the distance between pixel centres, 25.4 mm divided by the PPI. The physical width and height follow from the same triangle.

Advertised diagonals are often rounded, so results can differ slightly from a manufacturer’s figure.

Formula

Diagonal (px) = √(width² + height²)
PPI = diagonal (px) ÷ diagonal (in)
Dot pitch (mm) = 25.4 ÷ PPI
Width (in) = diagonal (in) × width (px) ÷ diagonal (px)

Worked example

A 24-inch 1920 × 1080 monitor has a diagonal of √(1920² + 1080²) = 2202.9 pixels, so 2202.9 ÷ 24 = 91.79 PPI, with a dot pitch of 0.2767 mm. The visible area is 53.13 × 29.89 cm.

Questions people ask

What is a good PPI?

It depends on viewing distance. Desktop monitors are often 90 to 160 PPI; phones, held closer, are usually 300 to 500 PPI.

Is PPI the same as DPI?

They are often used interchangeably. Strictly, PPI describes screen pixels and DPI describes printer dots.