PPI Calculator

Use this PPI calculator to find the pixel density of a display from its Width in pixels, Height in pixels, and Diagonal size in inches. The result includes PPI, aspect ratio, screen area in square inches, and pixel diagonal.

How to use this calculator

1. Enter the horizontal pixel count in Width.
2. Enter the vertical pixel count in Height.
3. Enter the physical diagonal in inches.
4. Review the PPI and related display metrics.

Width and height must be positive whole-pixel values. If you need to convert a physical screen dimension first, the length converter can help keep units consistent.

Formula

PPI = sqrt(width² + height²) / diagonal size

The calculator first finds the pixel diagonal, then divides by the physical diagonal size.

Worked example

For a 1920 × 1080 display with a 15.6 inch diagonal, the pixel diagonal is about 2202.91 pixels.

$2202.91 \div 15.6 = 141.21$

The display is about 141.21 PPI, with a 16:9 aspect ratio.

Interpreting PPI

PPI is most useful when comparing similar devices at similar viewing distances. A phone can need far higher PPI than a TV because it is held much closer. For image resizing and proportional dimensions, the scale converter calculator is a helpful companion, and the scientific notation calculator can format very large pixel counts.

Common mistakes

• Entering physical width instead of diagonal size.
• Mixing centimeters and inches.
• Assuming a resolution such as 4K guarantees high density.
• Comparing PPI without considering viewing distance.