Technology

PPI Calculator (Pixels Per Inch)

Calculate the pixels per inch (PPI) of any display from its resolution and diagonal size. Also shows dot pitch in millimetres and total megapixels.

PPI Calculator (Pixels Per Inch)

Horizontal resolution (px)

Vertical resolution (px)

Diagonal screen size (inches)

Method

How this calculator works

PPI = √(width_px² + height_px²) ÷ diagonal (inches). Dot pitch (mm) = 25.4 ÷ PPI. Megapixels = (width × height) ÷ 1,000,000.

Enter the horizontal resolution of your display in pixels (for example, 1920).
Enter the vertical resolution in pixels (for example, 1080).
Enter the diagonal screen size in inches (for example, 24).
The tool computes the diagonal resolution with the Pythagorean theorem, divides by the diagonal size, and reports PPI, dot pitch, and total megapixels.

Examples

Worked examples

Real numbers, end-to-end results.

1920 × 1080 on a 24-inch monitor

≈ 92 PPI

Diagonal pixels = √(1920² + 1080²) ≈ 2203, divided by 24 inches gives about 92 PPI.

2532 × 1170 on a 6.1-inch phone

≈ 460 PPI

A modern smartphone panel with a very fine dot pitch of about 0.055 mm.

Use cases

When to use it

Comparing the sharpness of two monitors or phones before buying.
Choosing a display that reaches the 'retina' threshold for your viewing distance.
Verifying manufacturer PPI claims from published resolution and size specs.
Estimating dot pitch for signage or kiosk displays viewed at a distance.

FAQ

Frequently asked questions

What is PPI (pixels per inch)?

PPI stands for pixels per inch. It measures how many pixels are packed into each linear inch of a display. A higher PPI means a sharper, more detailed image because individual pixels become harder to distinguish with the naked eye.

How is PPI calculated?

PPI is found by taking the diagonal resolution in pixels and dividing it by the diagonal screen size in inches. The diagonal resolution is the square root of the width squared plus the height squared: PPI = √(width² + height²) / diagonal inches.

What is a good PPI for a screen?

It depends on viewing distance. Smartphones typically range from 300 to 500+ PPI for crisp text held close to the eye. Laptops and monitors are usually comfortable around 100–220 PPI, while large TVs viewed from across a room can look great at 40–80 PPI.

What is dot pitch and how does it relate to PPI?

Dot pitch is the physical distance between the centres of adjacent pixels, usually given in millimetres. It is the inverse of pixel density: dot pitch (mm) = 25.4 / PPI. A smaller dot pitch means pixels are closer together and the image is sharper.

Does higher PPI always look better?

Not necessarily. Beyond a certain point—often called the 'retina' threshold for a given viewing distance—the human eye can no longer resolve individual pixels, so extra density yields no visible benefit while consuming more power and processing.