Free PPI Calculator - Pixels Per Inch from Resolution & Diagonal

PPI Calculator

Compute pixels per inch, dot pitch, and total megapixels for any display from resolution plus diagonal size.

Enter horizontal resolution, vertical resolution, and diagonal size (in inches). PPI = square root of (w² + h²) divided by the diagonal.

Common displays

Horizontal pixels

Vertical pixels

Diagonal (inches)

Pixels per inch (PPI)

163

Dot pitch

Aspect ratio

Total pixels

High density (150-220 PPI)

Tip: Apple considers a display "Retina" at roughly 220 PPI for laptops, 300 PPI for phones. Typical 1080p 24" monitors are ~92 PPI; 4K 27" is ~163 PPI.

Popular tools

All tools

Display Aspect Ratio Calculator Type any two of width, height, or ratio. Auto-simplifies to lowest integer terms and renders a live preview Open calculator

Display Screen Tester Detect dead, stuck, or hot pixels on screens Test your screen

Camera Webcam Tester Check webcam quality, resolution, and snapshots Test your webcam

Audio Hearing Age Test Mosquito tone hearing test - 12 frequencies from 8 kHz to 22 kHz to estimate your hearing age Test hearing age

PPI Calculator guide

How to use the PPI Calculator accurately

PPI stands for "pixels per inch" — how many physical display pixels fit into one inch of screen. It's computed from the resolution (horizontal × vertical pixels) and the diagonal size of the screen in inches.

01 What Is PPI? PPI stands for "pixels per inch" — how many physical display pixels fit into one inch of screen. It's computed from the resolution (horizontal × vertical pixels) and the diagonal size of the screen in inches.

02 How To Calculate PPI The formula is simple trigonometry. If the screen is w pixels wide and h pixels tall, the diagonal pixel count is √(w² + h²). Divide that by the diagonal size in inches to get PPI:

03 Retina and High-DPI Displays Apple popularized the term "Retina" for displays whose pixels are too small for the human eye to distinguish individually at normal viewing distance.

04 PPI vs DPI — What's The Difference? PPI refers to display pixels, DPI refers to dots printed on paper. They're measured the same way but describe different outputs.

ppi calculator pixels per inch calculator dpi calculator monitor dot pitch calculator screen density calculator PPI Calculator

PPI = √(w² + h²) / diagonal_in_inches

PPI Calculator FAQ

Common ppi calculator questions

How do I calculate pixels per inch?

Take the square root of (width² + height²) to get the diagonal in pixels, then divide by the diagonal size in inches. The tool does this live as you change any field.

What PPI counts as Retina or high-DPI?

Apple considers roughly 220 PPI for laptops and 300 PPI for phones as Retina. Above that, individual pixels are not distinguishable at normal viewing distance.

Is PPI the same as DPI?

Not quite. PPI is pixels per inch on a display, DPI is dots per inch in print. The math is identical but the output medium differs.

Why does my 4K 32-inch monitor feel less sharp than 4K 27-inch?

Because the 32-inch spreads the same 3840x2160 across a bigger area, so PPI drops from ~163 to ~138. Sit further back or accept softer text.

Checklist

Display checks to confirm

What Is PPI? PPI stands for "pixels per inch" — how many physical display pixels fit into one inch of screen. It's computed from the resolution (horizontal × vertical pixels) and the...
How To Calculate PPI The formula is simple trigonometry. If the screen is w pixels wide and h pixels tall, the diagonal pixel count is √(w² + h²).
Retina and High-DPI Displays Apple popularized the term "Retina" for displays whose pixels are too small for the human eye to distinguish individually at normal viewing distance.