1.The Mathematical Formula for PPI
Pixel density measures how many physical display pixels are packed into a single linear inch of screen space: PPI = sqrt(width^2 + height^2) / diagonal_inches. A 24" 1080p monitor has 91.79 PPI, a 27" 1440p monitor offers 108.79 PPI, and a 27" 4K monitor reaches 163.18 PPI.
2.Dot Pitch and Text Clarity
Dot pitch is the physical distance between the centers of two adjacent pixels (dot_pitch = 25.4 / PPI). Higher PPI results in smaller dot pitch (0.15mm vs 0.27mm), eliminating visible pixel grid "screen door" effects and rendering subpixel text with print-like sharpness.
Frequently Asked Questions
What is the sweet spot PPI for PC desktop monitors?
For standard 50–70cm viewing distances, 108 to 140 PPI (such as 27" 1440p or 32" 4K with 125% OS scaling) provides ideal sharpness without straining eyesight.
How do I calculate the PPI of my own screen?
Use the FPSRate PPI Calculator to enter your resolution and diagonal size or choose from built-in presets.