Work out screen pixel density (PPI) from the resolution and diagonal size.
Calculated locally in your browser.
How do you calculate screen PPI?
PPI = √(width² + height²) ÷ diagonal in inches, and dot pitch (mm) = 25.4 ÷ PPI. For example, a 1920 × 1080 screen with a 24-inch diagonal has √(1920² + 1080²) ÷ 24 ≈ 91.79 PPI and a 16:9 aspect ratio. A smaller diagonal packs the same pixels into less space, giving a higher, sharper PPI.
Understanding your result
Two screens with the same resolution can look very different: a smaller diagonal packs the same pixels into less space, giving a higher PPI and a sharper image. Always use the native resolution and the physical diagonal, not an upscaled or interface-scaled resolution.
Formula and method
PPI = √(width² + height²) ÷ diagonal in inches. Dot pitch (mm) = 25.4 ÷ PPI, since there are 25.4 mm in an inch.
Worked example
A 1920 × 1080 screen with a 24-inch diagonal has √(1920² + 1080²) ÷ 24 ≈ 91.79 PPI and a 16:9 aspect ratio.
How to use this tool
- Enter the horizontal resolution in pixels.
- Enter the vertical resolution in pixels.
- Enter the screen diagonal in inches.
- Read the PPI, dot pitch and aspect ratio.
Common mistakes to avoid
- Using a scaled resolution instead of the native one.
- Entering the diagonal in centimetres instead of inches.
- Confusing PPI (physical density) with DPI (a printing term).
About the PPI Calculator
The PPI Calculator finds a display's pixel density — pixels per inch — from its resolution and diagonal size. It also reports the dot pitch, total pixels and aspect ratio, so you can compare how sharp two screens really are.
Who should use this tool
Developers, designers, gamers and anyone comparing monitors, phones, laptops or TVs.
Benefits
- Pixel density (PPI) from resolution and screen size.
- Dot pitch in millimetres and total megapixels.
- Reduced aspect ratio such as 16:9.
- Private — calculated entirely in your browser.
Practical use cases
- Comparing the sharpness of two monitors.
- Checking whether a screen counts as "retina" or high-DPI.
- Choosing a display for design or photo work.
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Frequently asked questions
What is a good PPI?
Desktop monitors are often 90–110 PPI, while phones exceed 300 PPI. Higher PPI means a sharper image, but viewing distance also matters.
Is PPI the same as DPI?
Not quite. PPI describes pixels per inch on a screen; DPI describes ink dots per inch in printing. The terms are often used interchangeably but mean different things.
What is dot pitch?
Dot pitch is the distance between adjacent pixels, in millimetres. A smaller dot pitch means a denser, sharper display.