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Pixel Density calculator
Pixel density (PPI) tells you how sharp a screen is. Enter the resolution and screen size to find pixels per inch.
Pixel Density
PPI = √(w² + h²) / d · Screen Resolution
PPI = √(w² + h²) / diagonal | Pixels per Inch
Two screens with the same resolution are not equally sharp: spread those pixels over more inches and each one grows, and the image softens. Pixel density (PPI, pixels per inch) captures that in a single number. This calculator computes it from resolution and diagonal size.
How to use this calculator
- Enter the screen's horizontal and vertical resolution in pixels.
- Enter the diagonal size in inches.
- Press calculate to see the pixel density in PPI.
The distance rule behind "retina" claims
The eye stops distinguishing pixels at a density that depends on viewing distance: a phone held close needs 300 PPI or more to look perfectly sharp, while a television across the room looks sharp far below that. PPI is therefore only meaningful together with how far away the screen sits.
Frequently asked questions
How is PPI calculated?
Find the diagonal resolution in pixels (square root of width² + height²) and divide by the diagonal size in inches.
What PPI is considered sharp?
For phones, about 300 PPI and up is effectively sharp at normal distance. Monitors typically run 90 to 160 PPI and are viewed further away.
Is higher PPI always better?
Only up to the point the eye can resolve at that distance. Beyond it, extra pixels buy little visible sharpness while costing processing power and battery.