How to use the Screen PPI Calculator
- Choose a device preset or type the screen's width and height in pixels. Use the long side as width.
- Enter the diagonal size in inches, as advertised by the manufacturer.
- Optionally add the device pixel ratio to see the CSS viewport size.
- Read the PPI, aspect ratio, physical size and pixel pitch below the form.
What PPI means and how it is calculated
PPI (pixels per inch) measures how many pixels fit along one inch of the screen. It is the diagonal resolution in pixels, calculated as the square root of width squared plus height squared, divided by the diagonal size in inches. A higher PPI means finer detail and less visible pixel structure at the same viewing distance.
The aspect ratio describes the shape of the screen. Many phones use ratios close to 19.5:9 or 20:9, while monitors are often 16:9 or 16:10. The tool simplifies your width and height and also shows the decimal value so unusual panels are easy to compare.
The device pixel ratio tells browsers how many physical pixels make up one CSS pixel. Dividing the resolution by it gives the viewport size your CSS sees. To check your own device live, use the Screen Size Checker, and convert sizes for your stylesheet with the PX to REM Converter.
Frequently asked questions
How do you calculate PPI?
Take the square root of (width in pixels squared plus height in pixels squared) to get the diagonal in pixels, then divide by the diagonal in inches. A 2556 × 1179 display at 6.1 inches comes out near 460 PPI.
What is a good PPI for a phone or monitor?
Phones are commonly above 400 PPI, while desktop monitors are often between 90 and 160 PPI. What looks sharp depends on your viewing distance, so closer screens need a higher PPI.
Is PPI the same as DPI?
They are often used interchangeably, but PPI describes screen pixels and DPI describes printed dots. For displays, PPI is the correct term.
Why is the aspect ratio shown as a decimal too?
Many modern screens have unusual ratios that do not simplify to small whole numbers. The decimal makes it easy to compare them against common ratios such as 16:9 (1.78) or 20:9 (2.22).