PPI Calculator
Enter a screen’s resolution and diagonal size to find its pixel density in pixels per inch, its dot pitch and its physical width and height.
PPI formula
PPI = √(width pixels² + height pixels²) ÷ diagonal inches
Pixels per inch measures how sharp a screen looks. The higher the PPI, the smaller each pixel and the crisper the text.
Worked example
A 24-inch 1920 × 1080 monitor has a pixel diagonal of √(1920² + 1080²) = 2,202.9, so its density is 2,202.9 ÷ 24 = 91.8 PPI. A 27-inch 2560 × 1440 monitor is about 108.8 PPI.
Typical pixel densities
| Device | Typical PPI |
|---|---|
| 24 in 1080p monitor | About 92 |
| 27 in 1440p monitor | About 109 |
| 27 in 4K monitor | About 163 |
| Modern smartphones | 400–500+ |
Frequently asked questions
What is a good PPI for a monitor?
Around 90–110 PPI suits normal scaling at desk distance; 140 and above looks very sharp.
Is PPI the same as DPI?
They are often used interchangeably, but DPI strictly refers to printer dots.
Does viewing distance matter?
Yes. Screens viewed from farther away, like TVs, need a lower PPI to look sharp.
What is dot pitch?
The distance between pixel centers, the inverse of pixel density.
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