Screen Resolution Converter
Calculate pixels per inch (PPI) from screen diagonal and resolution.
Compare monitors, phones, and tablets to see how Retina and 4K displays differ.
Enter your screen resolution and size to calculate pixel density.
PPI (Pixels Per Inch) measures how sharp a screen appears. Higher PPI means more detail and smoother text.
Formula: PPI = √(width_px² + height_px²) ÷ diagonal_inches
The diagonal in pixels is calculated using the Pythagorean theorem. Then divided by the physical screen diagonal in inches.
DPCM (Dots Per Centimeter):
- DPCM = PPI ÷ 2.54
Common device PPI values:
| Device | Resolution | Size | PPI |
|---|---|---|---|
| 24" Monitor | 1920×1080 | 24" | 92 |
| 27" 4K Monitor | 3840×2160 | 27" | 163 |
| MacBook Pro 14" | 3024×1964 | 14.2" | 254 |
| iPhone 15 | 2556×1179 | 6.1" | 460 |
| iPad Pro 12.9" | 2732×2048 | 12.9" | 264 |
Sharpness guidelines:
- Under 100 PPI: visible pixels at arm’s length
- 100–150 PPI: standard desktop monitors
- 150–250 PPI: “Retina” quality at normal viewing distance
- Over 300 PPI: print-quality sharpness (smartphones)