How to Calculate PPI

PPI — pixels per inch — measures how densely pixels are packed on a display.

The formula

1. Diagonal pixels = sqrt(Width² + Height²).
2. PPI = Diagonal pixels / Diagonal size in inches.

Worked example

A 1920 × 1080 monitor at 24 inches: diagonal pixels = sqrt(1920² + 1080²) ≈ 2203. PPI = 2203 / 24 ≈ 92 PPI.

The same resolution on a 15.6-inch laptop gives about 141 PPI, which is why laptop text looks sharper than the same resolution on a large monitor.

What PPI means in practice

Higher PPI means smaller, sharper-looking pixels at the same viewing distance. But viewing distance matters: a phone held close needs higher PPI than a TV viewed from across a room to look equally sharp.

Try it: PPI Calculator · Monitor PPI Calculator · Screen Size Calculator