PPI Explained
Complete guide to understanding pixels per inch and how it affects display sharpness. Learn how PPI impacts TVs, monitors, and phones.
What is PPI?
PPI (Pixels Per Inch) measures the pixel density of a display - specifically, how many pixels fit into one linear inch of screen space. It's a critical factor in determining how sharp and clear a display appears to the human eye.
Why PPI Matters
- 1 Sharpness: Higher PPI = sharper image
- 2 Visibility: Lower PPI may show visible pixels
- 3 Viewing Distance: Impact varies by proximity
Visual Comparison
Low PPI (100)
High PPI (300+)
How to Calculate PPI
The PPI Formula
PPI is calculated using the Pythagorean theorem to find the diagonal pixel count, then dividing by the screen diagonal in inches.
Example: 1080p Monitor
- • Resolution: 1920 × 1080 pixels
- • Screen Size: 24 inches
- • Calculation: √(1920² + 1080²) ÷ 24
- • Result: 2203 ÷ 24 = 92 PPI
Example: 4K TV
- • Resolution: 3840 × 2160 pixels
- • Screen Size: 55 inches
- • Calculation: √(3840² + 2160²) ÷ 55
- • Result: 4406 ÷ 55 = 80 PPI
PPI Calculator Tool
Use our Screen Size Calculator to automatically compute PPI for your device with our interactive tool.
Resolution PPI Comparison
| Resolution | 24\" PPI | 27\" PPI | 32\" PPI |
|---|---|---|---|
| 1080p (1920x1080) | 92 | 82 | 69 |
| 1440p (2560x1440) | 122 | 109 | 92 |
| 4K (3840x2160) | 183 | 163 | 138 |
PPI Quality Categories
| Category | PPI Range | Quality Description | Typical Devices |
|---|---|---|---|
| Low Resolution | 50-100 PPI | Visible pixels, acceptable at distance | Budget TVs, older displays |
| Standard Definition | 100-150 PPI | Acceptable for normal viewing | Most 1080p TVs, basic monitors |
| High Definition | 150-250 PPI | Good clarity and sharpness | 1440p monitors, some 4K TVs |
| Retina/HiDPI | 250-400 PPI | Sharp, no visible pixels | High-end laptops, tablets |
| Ultra High Definition | 400+ PPI | Exceptional sharpness | Flagship phones, premium displays |
PPI by Device Type
TVs
- 1080p (40\") 54 PPI
- 4K (55\") 80 PPI
- 4K (65\") 68 PPI
- 8K (75\") 110 PPI
For TVs, viewing distance reduces need for very high PPI. At 8-12 feet, 50-100 PPI is sufficient.
Monitors
- 1080p (24\") 92 PPI
- 1440p (27\") 109 PPI
- 4K (27\") 163 PPI
- 4K (32\") 138 PPI
For monitors at 2-3 feet distance, 100+ PPI is recommended for sharp text and images.
Phones
- 1080p (6.1\") 426 PPI
- iPhone 14 Pro 460 PPI
- Galaxy S23 Ultra 506 PPI
- iPad Pro (12.9\") 265 PPI
For phones at 10-12 inch distance, 300+ PPI is needed to avoid visible pixels (Retina quality).
PPI and Viewing Distance
The Relationship Between Distance and Required PPI
Close Viewing
Phones, AR/VR (10-20\")
300+ PPI needed
Medium Distance
Monitors, tablets (2-3 feet)
100-150+ PPI needed
Far Viewing
TVs, projectors (8+ feet)
50-100+ PPI sufficient
The closer you are to a screen, the higher the PPI needed to prevent visible pixels and maintain image quality.
The Acuity Limit
The human eye can distinguish detail up to a certain limit, known as visual acuity. At typical viewing distances, there's a PPI threshold beyond which additional pixels provide no visible benefit:
- At arm's length (24 inches): ~87 PPI is the acuity limit
- At tablet distance (15 inches): ~140 PPI is the acuity limit
- At phone distance (12 inches): ~175 PPI is the acuity limit
- At TV distance (9 feet for 65\" TV): ~11 PPI is the acuity limit
This means that extremely high PPI on large screens viewed from distance provides no benefit to the viewer.
Practical Applications of PPI
Choosing a TV
For TVs, PPI is less critical due to viewing distance. Focus on resolution compatibility and screen size relative to room.
- • 4K recommended for 55\"+
- • 1080p OK for 40\"-50\"
- • Consider viewing distance
Selecting a Monitor
For monitors, 100+ PPI ensures sharp text and detailed work. Balance resolution with screen size.
- • 1440p on 27\" = 109 PPI
- • 4K on 27\" = 163 PPI
- • Higher PPI = more GPU demand
Phone Screen Quality
Phones need 300+ PPI to prevent visible pixels. Most flagships exceed this threshold.
- • Minimum 300 PPI for "Retina"
- • Most phones have 400-500+ PPI
- • Higher PPI = higher battery usage
Gaming Considerations
Higher PPI provides more detailed images but requires more GPU power to maintain frame rates.
- • Balance PPI with performance
- • Higher resolutions = more GPU demand
- • Consider refresh rates too
Photo/Video Editing
Accurate color and sharp detail are crucial. Higher PPI helps see fine details in images.
- • 150+ PPI for detailed work
- • Consider color accuracy too
- • Larger screens often preferred
Eye Strain Prevention
Lower PPI screens can cause eye strain due to visible pixels and text aliasing.
- • Higher PPI reduces eye strain
- • Sufficient PPI for viewing distance
- • Consider screen brightness too
Related Screen Tools
TV Screen Size Calculator
Calculate PPI and viewing distance for your TV setup.
Monitor Screen Size Calculator
Find ideal monitor size and PPI for your desk setup.
Projector Screen Size Calculator
Calculate throw distance and ratio for your projector setup.
Phone Screen Size Calculator
Determine PPI and pixel density for your phone screen.