PPI (Pixel Density) Calculator

About the PPI (Pixel Density) Calculator

Pixel density (PPI) is how many pixels fit per inch of display. Higher PPI means sharper images. It is found from the pixel resolution and the physical diagonal size.

How to use

Enter horizontal and vertical resolution in pixels and the screen diagonal in inches, then click Calculate.

Worked example

1920x1080 on a 15.6-inch screen gives about 141 PPI.

How to use this calculator

1. Enter the screen resolution in pixels as width and height.
2. Enter the screen size as the diagonal in inches.
3. Click calculate to get the pixels per inch value.
4. Use the result to compare how sharp different screens may look.

The formula explained

• \(\text{PPI}\) = pixels per inch, the display density
• \(w\) = screen width in pixels
• \(h\) = screen height in pixels
• \(d\) = screen diagonal in inches

Step by step method

1. Find the screen resolution, such as 1920 by 1080.
2. Square the width and height, then add those values together.
3. Take the square root of that sum to get the diagonal pixel count.
4. Divide the diagonal pixel count by the screen diagonal in inches.

Worked example

Suppose you want to find the pixel density of a 24 inch monitor with a 1920 by 1080 resolution.

1. Use the formula \(\text{PPI} = \frac{\sqrt{w^2 + h^2}}{d}\) with \(w = 1920\), \(h = 1080\), and \(d = 24\).
2. Calculate the diagonal in pixels: \(\sqrt{1920^2 + 1080^2} = \sqrt{3686400 + 1166400} = \sqrt{4852800} = 2202.91\).
3. Divide by the diagonal size: \(2202.91 \div 24 = 91.79\).

Tips and common mistakes

• Make sure you enter the width and height in pixels, not in physical units.
• Use the diagonal size of the screen in inches, not the width or height.
• If you swap width and height on a rotated screen, the PPI stays the same, but the numbers should still match the actual resolution.
• PPI describes density, not overall image quality by itself. Viewing distance and panel type also matter.

Frequently asked questions