PPI Calculator
Find how tightly a display packs its pixels — its pixel density, in pixels per inch — from its resolution and size.
Resolution
Resolution is how many pixels the screen shows across and down — 2560 × 1440, for example. It is normally in the specification, or in your display settings.
Common resolutions
Physical size
Enter the advertised screen size: the diagonal, measured corner to corner.
Common diagonals
Pixel density (PPI)
108.8PPI
PPI means pixels per inch. This screen fits about 108.8 pixels into every inch, so neighbouring pixel centres sit 0.233 mm apart. A higher PPI means the pixels are packed more tightly; how fine that looks also depends on how far away you sit.
Pixel density 108.8 pixels per inch.
Pixel pitch
Details
- Pixels per centimetre42.8 PPCM
- Pixel pitch0.233 mm
- Display width23.53 in59.77 cm
- Display height13.24 in33.62 cm
- Total pixels3,686,400
- Megapixels3.69 MP
- Resolution aspect ratio16:9Exact simplified ratio
Formula and assumptions
diagonalInchesequalsdiagonal converted to inches (1 inch = 25.4 mm exactly)
Density from the resolution and the diagonal
pixelDiagonalequals√(pixelWidth² + pixelHeight²)
PPIequalspixelDiagonal ÷ diagonalInches
pixelPitchMmequals25.4 ÷ PPI
PPCMequalsPPI ÷ 2.54
Physical size of the active area
displayWidthequalspixelWidth ÷ PPI
displayHeightequalspixelHeight ÷ PPI
Assumptions
- Pixels are assumed to be square.
- The physical active area is assumed to have the same proportions as the resolution you entered.
- PPI is a measurement, not a quality rating. No verdict such as “good” or “retina” is applied to it.
- Physical width and height are derived from the resolution and the calculated density, so they describe the active display area only.
Questions
What does PPI actually measure?
PPI is pixels per inch: how many pixels sit along one inch of the display. It describes how finely the picture is divided, not how good the screen is. Two screens with the same PPI can differ enormously in colour, contrast and brightness.
Is a higher PPI always better?
Not necessarily. What matters is the angular size of a pixel as you see it, which depends on both density and viewing distance. A television viewed from three metres does not need the density of a phone held at arm’s length. Ratio & Rule reports the measurement and leaves the judgement to you.
What is pixel pitch?
Pixel pitch is the distance between the centres of neighbouring pixels, usually given in millimetres. It is the inverse of density: as PPI rises, pitch falls. At 100 PPI the pitch is 0.254 mm.
Should I use PPI or DPI for a screen?
PPI. DPI describes ink dots a printer places on paper. Screens have pixels, so PPI is the accurate term, even though many tools label the same calculation DPI.
Why does the calculated physical width differ slightly from the specification?
The calculation assumes square pixels and an active area whose physical proportions match the resolution you entered. That is true of nearly all modern displays, but a panel with non-square pixels will differ.