DPI / PPI Calculator

Work out the pixel density (PPI) of any screen from its resolution and diagonal, or switch to print mode to see your print's size and quality at 150, 240, 300 or 600 DPI.

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Pixel density
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Quick examples

How DPI and PPI are calculated

Pixel density is the diagonal in pixels divided by the physical diagonal in inches:

PPI = √(width² + height²)diagonal (inches)

For screens we use that formula: more pixels on the same diagonal means more sharpness. For printing, the maths runs in reverse: print size = pixels ÷ DPI. Printing at 300 DPI gives results that are sharp up close; lowering the DPI enlarges the print but reduces quality. The tool also gives the dot pitch (mm per pixel) and megapixels.

Example: calculating a screen's PPI

A 1920 × 1080 monitor at 24″:

  • Diagonal in pixels = √(1920² + 1080²) ≈ 2202 px.
  • 2202 ÷ 24 ≈ 92 PPI (medium density, typical for a monitor).

In print: a 6000 × 4000 px photo at 300 DPI prints at 20 × 13.3″ (≈ 51 × 34 cm) at excellent quality.

DPI and PPI FAQ

What's the difference between DPI and PPI?
PPI (pixels per inch) measures the pixel density of a screen; DPI (dots per inch) is used in printing. In practice many people use them interchangeably: both describe how many dots/pixels fit in one inch.
How do I calculate a screen's PPI?
Divide the diagonal in pixels (square root of width² + height²) by the physical diagonal in inches. For example, 1920×1080 on 24″ ≈ 92 PPI. The calculator does it for you in Screen mode.
What DPI do I need for a quality print?
The sharp-print standard is 300 DPI; 240 DPI gives good results, and at large sizes (posters viewed from afar) 150 DPI can be enough. Print mode tells you the maximum size at each DPI.
What is a "Retina" display?
It is a marketing term for high densities (≈220-460 PPI) where, at normal viewing distance, the eye cannot resolve individual pixels. The calculator flags anything above ~300 PPI as "Retina".
How many megapixels do I need for a poster?
Multiply the desired size in inches by the target DPI. A 24×16″ poster at 300 DPI needs 7200×4800 px ≈ 34.6 MP; at 150 DPI, a quarter of that. Use Print mode in reverse.