Calculators
Pixel Density Calculator (PPI)
Two screens with the same resolution can look completely different. A 3840×2160 panel is astonishingly sharp on a 15-inch laptop and merely normal on a 43-inch monitor, because density, not raw resolution, determines what your eye resolves.
Enter a resolution and a diagonal measurement to get the pixel density in PPI.
Pixel density
141.2 PPI
Diagonal resolution
2203 px
Dot pitch
0.180 mm
How to use this tool
- 1Enter the horizontal and vertical resolution of the display.
- 2Enter the diagonal size in inches.
- 3Read the calculated pixels-per-inch figure.
- 4Compare it against typical values below to judge sharpness.
How the calculation works
Pythagoras gives the diagonal in pixels: the square root of width squared plus height squared. Dividing that by the diagonal in inches gives PPI. A 2560×1440 27-inch monitor works out at roughly 109 PPI.
Typical densities
Standard desktop monitors sit between 90 and 110 PPI. Retina-class laptops are around 220. Modern phones run from 400 to over 500, which is why phone screenshots look so large when opened on a desktop. Televisions are low, often near 50 PPI, but viewing distance compensates.
Why this matters for images
High-density screens draw two or three device pixels for every CSS pixel, so an image displayed 400 px wide needs an 800 px source to look sharp on a 2× display. That is the reasoning behind responsive srcset markup: serve the larger file only to the devices that can use it.
Frequently Asked Questions
Is higher PPI always better?
Beyond roughly 300 PPI at phone viewing distance, most people cannot see individual pixels, so gains become theoretical while power draw rises.
Does PPI depend on viewing distance?
The number does not, but perceived sharpness does. A television at 50 PPI looks fine across a room.
What is a retina display?
A marketing term for a screen dense enough that pixels are not individually visible at typical viewing distance. There is no single threshold.
How does this relate to DPI for printing?
The maths is identical; only the medium changes. Screens are measured in PPI, printed output in DPI.