Category
Tech
Screen Size / PPI Calculator
Calculate PPI and density class from display resolution and diagonal size
Estimated time
1 min
Display Inputs
Enter horizontal and vertical resolution plus screen diagonal size in inches.
Horizontal pixel count of the panel. Use native resolution values when possible.
Vertical pixel count of the panel. Pair this with width and diagonal to compute PPI.
Physical screen size measured diagonally in inches. This value is required to convert pixel counts into PPI.
Quick presets
Formula Summary
Pixel diagonal (px) = sqrt(width^2 + height^2)
PPI = pixel diagonal / diagonal inches
Dot pitch (mm) = 25.4 / PPI
Density class: Low < 110, Standard 110 to 219.99, Retina >= 220
How It Works
This calculator estimates pixel density from screen resolution and physical diagonal size. Pixel density is commonly expressed as pixels per inch (PPI).
Higher PPI means smaller and more tightly packed pixels, which generally produces sharper text and graphics at normal viewing distances.
- Pixel diagonal (px) = sqrt(width^2 + height^2).
- PPI = pixel diagonal / diagonal inches.
- Dot pitch (mm) = 25.4 / PPI.
- Density classes in this calculator: Low < 110 PPI, Standard 110 to 219.99 PPI, Retina >= 220 PPI.
- Class thresholds are planning guidance, not strict quality guarantees because viewing distance and scaling also matter.
Example Calculations
24-inch 1080p monitor
Resolution 1920 x 1080, diagonal 24 in
Pixel diagonal 2202.91 px, PPI 91.79 -> Low density class
24-inch 1440p monitor
Resolution 2560 x 1440, diagonal 24 in
Pixel diagonal 2937.21 px, PPI 122.38 -> Standard density class
6.1-inch smartphone panel
Resolution 2556 x 1179, diagonal 6.1 in
Pixel diagonal 2814.81 px, PPI 461.44 -> Retina density class
Frequently Asked Questions
What does PPI actually tell me?
PPI indicates how many pixels fit into each inch of screen. Higher PPI usually means sharper edges, smoother fonts, and less visible pixel structure.
Is Retina a strict technical standard?
No. Retina is a marketing term. This calculator uses a practical threshold of 220 PPI or more to label a display as retina class.
Why does the same PPI look different on different devices?
Viewing distance, operating-system scaling, subpixel layout, panel type, and anti-aliasing all affect perceived sharpness.
Should I optimize for PPI only when buying a display?
PPI is important, but also check brightness, contrast, color gamut, refresh rate, and ergonomic factors for your specific use case.
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