When shopping for a new monitor, TV, or phone, you'll encounter terms like "4K," "1080p," and "Retina display." But resolution alone doesn't tell the whole story. What really matters for visual clarity is Pixel Density, measured in PPI (Pixels Per Inch).
What is PPI?
PPI measures how many pixels are packed into one inch of screen space. Higher PPI means:
- Sharper text and images
- Less visible pixel grid ("screen door effect")
- Better detail in photos and videos
How PPI is Calculated
The formula for PPI is:
PPI = √(width² + height²) ÷ diagonal screen size
For example, a 27-inch 1080p monitor:
PPI = √(1920² + 1080²) ÷ 27
PPI = √(3,686,400 + 1,166,400) ÷ 27
PPI = 2203 ÷ 27
PPI ≈ 82
PPI Guidelines by Use Case
For Desktop Monitors (Viewing Distance: 2-3 feet)
| PPI Range | Quality | Recommendation |
|---|---|---|
| Below 90 | Low | Avoid for text work |
| 90-110 | Acceptable | Budget option |
| 110-140 | Good | Sweet spot for most users |
| 140+ | Excellent | Professional/Retina quality |
Common Monitor Configurations
| Size | Resolution | PPI | Verdict |
|---|---|---|---|
| 24" | 1080p | 92 | Good for gaming |
| 27" | 1080p | 82 | Text looks fuzzy |
| 27" | 1440p | 109 | Sweet spot |
| 27" | 4K | 163 | Excellent, may need scaling |
| 32" | 1440p | 92 | Acceptable |
| 32" | 4K | 138 | Excellent |
The "Retina" Standard
Apple coined the term "Retina display" for screens where individual pixels are indistinguishable at typical viewing distance. The threshold depends on distance:
- Phone (10-12 inches): ~300 PPI
- Tablet (15-18 inches): ~260 PPI
- Laptop (18-24 inches): ~220 PPI
- Desktop (24-30 inches): ~110 PPI
Why 1080p on 27" Looks Bad
A 27-inch 1080p monitor has only 82 PPI. At typical desktop viewing distance (2 feet), you can clearly see individual pixels, especially in:
- Small text
- Thin lines
- UI elements
This is why many professionals recommend 1440p as the minimum for 27-inch monitors.
4K: Is It Worth It?
4K (3840×2160) offers excellent PPI on most screen sizes, but consider:
Pros:
- Crystal clear text and images
- Future-proof for content
- Great for photo/video editing
Cons:
- Requires powerful GPU for gaming
- May need UI scaling (125-150%)
- More expensive
Practical Recommendations
For Gaming
- 24" 1080p (92 PPI) - Good balance of performance and clarity
- 27" 1440p (109 PPI) - Best overall experience
- 32" 4K (138 PPI) - Premium choice
For Productivity/Coding
- 27" 1440p minimum - Text clarity is crucial
- 27" 4K with scaling - Best for long work sessions
- 32" 4K - More screen real estate
For Photo/Video Editing
- 27" 4K or higher - Color accuracy and detail matter
- Consider wide-gamut panels (Adobe RGB, DCI-P3)
Conclusion
Don't just look at resolution—consider PPI for your specific screen size. Use our PPI Calculator to find the pixel density of any display configuration and make informed purchasing decisions.
Remember: A 4K TV looks great from the couch, but a 4K monitor at desk distance is a completely different experience!