DPI/PPI Calculator
Calculate screen DPI/PPI from resolution and size. Find optimal viewing distance for monitors and TVs. Reverse calculate resolution from desired DPI. Perfect for monitor shopping and display setup.
Table of Contents
What is DPI/PPI?
**DPI (Dots Per Inch)** and **PPI (Pixels Per Inch)** are measurements of pixel density — how many pixels (or dots) are packed into one inch of screen space. While technically different (DPI refers to print, PPI refers to screens), they're often used interchangeably for displays.
Higher DPI/PPI means more pixels per inch, resulting in:
- Sharper images — More detail and clarity
- Smaller pixels — Less visible pixelation when viewed up close
- Better text rendering — Smoother fonts and sharper edges
- Closer viewing — Can sit closer without seeing individual pixels
Common DPI/PPI ranges:
- 72-96 PPI — Older displays, large TVs viewed from distance
- 100-110 PPI — Standard desktop monitors (24-27" 1080p)
- 140-160 PPI — High-end monitors, laptops (27" 1440p, 15" 1080p)
- 200+ PPI — Retina displays, high-end 4K monitors, smartphones
How it Works
The DPI/PPI calculation uses the Pythagorean theorem to determine the diagonal pixel count, then divides by the screen's diagonal size in inches.
Standard Calculation
To calculate DPI/PPI from screen specifications:
1. Calculate diagonal pixels: √(width² + height²)
2. Calculate PPI: diagonal pixels ÷ diagonal inches
Example: 27" monitor with 2560 × 1440 resolution
Diagonal pixels = √(2560² + 1440²) = √(6,553,600 + 2,073,600) = √8,627,200 = 2,937 pixels
PPI = 2,937 ÷ 27 = 108.8 PPI
Reverse Calculation
To find the missing resolution dimension from desired DPI:
1. Calculate total diagonal pixels: DPI × diagonal inches
2. Calculate missing dimension: √(diagonal pixels² - known dimension²)
This is useful when shopping for monitors — you know the size and desired pixel density, but need to determine what resolution to look for.
Optimal Viewing Distance
The optimal viewing distance depends on your display's pixel density. Higher PPI displays allow you to sit closer without seeing individual pixels, while lower PPI displays require more distance for a smooth viewing experience.
High PPI (200+ PPI)
Retina displays, high-end 4K monitors, smartphones. You can sit very close (1-1.5× screen height) and still see a crisp, pixel-free image. Perfect for detailed work, text editing, and close-up viewing.
Medium PPI (100-200 PPI)
Standard desktop monitors, laptops, 1080p/1440p displays. Optimal distance is 1.5-2.5× screen height. At this distance, individual pixels blend together for a smooth viewing experience. This is the sweet spot for most desktop work.
Lower PPI (<100 PPI)
Large TVs, projectors, older displays. Requires more distance (2.5-3.5× screen height) to avoid seeing individual pixels. Perfect for media consumption from a distance, but not ideal for close-up work.
Tip: For desktop monitors, aim for 100+ PPI if you'll be sitting within 2-3 feet of the screen. For TVs, lower PPI is acceptable since viewing distance is typically much greater.
Common Use Cases
- Monitor Shopping: Compare pixel density between different monitor models to ensure sharp image quality for your use case
- TV Selection: Determine optimal viewing distance for 4K vs 1080p TVs to see if you'll notice the difference from your seating position
- Workspace Setup: Calculate ideal monitor placement and viewing distance based on your display's PPI
- Multi-Monitor Setup: Ensure consistent pixel density across multiple displays for seamless workflow
- Resolution Planning: Use reverse calculator to determine what resolution you need for a specific screen size and desired pixel density
- Retina Display Understanding: Understand what makes a "retina" display and whether your setup qualifies
- Gaming Setup: Balance resolution, screen size, and pixel density for optimal gaming experience
- Design Work: Ensure your display has sufficient pixel density for detailed graphic design, photo editing, or video work
Examples
Example 1: 27" 1440p Monitor
Input: 27" diagonal, 2560 × 1440 resolution
Calculation: √(2560² + 1440²) ÷ 27 = 2,937 ÷ 27 = 108.8 PPI
Result: 108.8 PPI — Excellent pixel density for desktop use. Optimal viewing distance: 20-30 inches (51-76 cm).
Example 2: 55" 4K TV
Input: 55" diagonal, 3840 × 2160 resolution
Calculation: √(3840² + 2160²) ÷ 55 = 4,400 ÷ 55 = 80 PPI
Result: 80 PPI — Lower pixel density suitable for viewing from distance. Optimal viewing distance: 60-84 inches (152-213 cm) or 5-7 feet away.
Example 3: Reverse Calculation
Goal: Find resolution for 32" monitor with ~110 PPI and 2560px width
Input: Desired DPI = 110, Diagonal = 32", Known width = 2560
Result: Calculated height ≈ 1440px, Resolution = 2560 × 1440
This confirms that a 32" 2560 × 1440 monitor has approximately 110 PPI, which is ideal for desktop use.
Frequently Asked Questions
DPI (Dots Per Inch) traditionally refers to print resolution, while PPI (Pixels Per Inch) refers to screen resolution. For digital displays, they're often used interchangeably since both measure pixel density. Our calculator uses both terms to match common terminology.
Apple defines "Retina" as displays where individual pixels cannot be discerned at a normal viewing distance, which typically means 200+ PPI for close-up viewing (phones, laptops) or 110+ PPI for desktop viewing distances. In practice, 100-110 PPI is excellent for desktop monitors, while 200+ PPI provides retina-quality for mobile devices.
Not necessarily. Higher PPI provides sharper images but also requires more GPU power to drive. For desktop monitors, 100-140 PPI is the sweet spot balancing sharpness and performance. Very high PPI (200+) is great for close-up viewing but may not be noticeable at typical desktop distances. For TVs viewed from distance, lower PPI (70-90) is perfectly fine.
Yes! PPI calculation works the same for curved monitors. The curvature doesn't affect pixel density — it only changes the viewing experience. Use the flat screen dimensions and resolution as you would for a flat monitor.
The viewing distance recommendations are estimates based on pixel density and typical viewing preferences. Actual optimal distance varies by individual vision, use case, and personal preference. Higher PPI allows closer viewing, but comfort is also important — adjust based on what feels comfortable for your eyes.
Prioritize PPI (pixel density) rather than resolution or size alone. A 27" 1440p monitor (109 PPI) often provides a better experience than a 32" 1080p monitor (69 PPI) for desktop work, even though the larger screen has more pixels total. For gaming, you may prioritize resolution and size based on performance considerations, but for productivity, PPI is key.
Yes! Ultrawide monitors work the same way. Enter the diagonal size and resolution (like 3440 × 1440). The calculator uses the Pythagorean theorem to calculate diagonal pixels, which works regardless of aspect ratio. For example, a 34" ultrawide with 3440 × 1440 resolution has approximately 110 PPI.
No. All calculations are performed locally in your browser. We don't store, save, or transmit any information. Your privacy is protected.