How to Calculate Pixel Density
What is Pixel Density?
A pixel density (PPI — pixels per inch) calculator determines screen sharpness from resolution and physical display size. Higher PPI = sharper image, less visible pixelation.
Formula
PPI = √(width² + height²) / diagonal(inches); DPI ≈ PPI for screen density; higher = sharper
- PPI
- Pixels Per Inch (pixels/inch)
- d
- Diagonal screen size (inches)
- w, h
- Screen resolution (pixels)
Step-by-Step Guide
- 1PPI = √(W² + H²) / diagonal (inches)
- 2W, H = horizontal and vertical resolution in pixels
- 3Apple Retina display threshold: ~300 PPI at arm's length
- 4TVs viewed from further away can be acceptable at 40–80 PPI
Worked Examples
Input
1920×1080 (Full HD) on 24" monitor
Result
PPI = √(1920²+1080²)/24 = √(3,686,400+1,166,400)/24 = √4,852,800/24 ≈ 91.8 PPI
Frequently Asked Questions
What's a good PPI?
Phone: 300+ PPI (retina). Laptop: 150-200 PPI. Desktop: 90-110 PPI. Higher = crisper text/images.
Why does screen size affect PPI?
Same resolution on larger screen spreads pixels farther apart = lower PPI. 1920×1080 at 24" vs 27" looks different.
How do I calculate if my screen is sharp enough?
Calculate PPI from resolution and diagonal. If >150 PPI, text is crisp. <90 PPI may show pixelation.