DPI / PPI calculator

Pixel density measures how many pixels fit into one inch of a display. Higher density means sharper text and images at the same viewing distance. This calculator works out pixels per inch (PPI) from a screen's resolution and diagonal size, which is useful when comparing monitors, phones and laptops.

How to use it

1. Enter the horizontal and vertical resolution, for example 3840 × 2160.
2. Enter the diagonal screen size in inches.
3. Read the PPI and the dot pitch.

The formula

Diagonal in pixels = √(width² + height²). PPI = diagonal pixels / diagonal inches.

Examples

• 27-inch 2560 × 1440 monitor: √(2560² + 1440²) = 2937 px, so 109 PPI.
• 27-inch 3840 × 2160 (4K) monitor: 4406 / 27 = 163 PPI.
• 24-inch 1920 × 1080 monitor: 92 PPI.
• 6.1-inch phone at 2556 × 1179: about 460 PPI.

PPI vs. DPI

PPI describes pixels on a screen or in a digital image. DPI (dots per inch) describes how densely a printer places ink dots. The terms are often mixed up. For printing, an image's PPI setting determines its physical size: a 3000 × 2000 px photo printed at 300 PPI is 10 × 6.67 inches.

How much density do you need?

• Desktop monitors at arm's length look sharp from about 110 PPI, and very sharp at 160 PPI and above with scaling.
• Phones are held closer, so they use 400 PPI or more.
• Print quality photos typically use 300 PPI.