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PPI Calculator

Calculate your screen's pixel density (PPI) in seconds

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Enter your screen's horizontal and vertical resolution in pixels, for example 1920 and 1080.
  2. 2.Enter the diagonal screen size in inches, for example 24, or tap a preset such as 1080p 24".
  3. 3.Read the results: PPI, dot pitch, pixels per cm and aspect ratio update instantly as you type.

About PPI Calculator

PPI (pixels per inch), also called pixel density, measures how many individual pixels are packed into one inch of a display. It is the single best number for comparing the sharpness of two screens: a phone and a TV can both be “1080p”, yet the phone looks far crisper because the same pixels are squeezed into a much smaller area. This free PPI calculator turns three simple inputs — horizontal resolution, vertical resolution and diagonal size — into pixel density and several related figures, right in your browser with nothing to install and nothing uploaded.

The math is short. First the pixels-per-inch calculator finds the diagonal length in pixels using the Pythagorean theorem, √(width² + height²). Dividing that by the diagonal size in inches gives the PPI. For a 1920×1080 panel measured at 24 inches the diagonal is about 2,202.9 pixels, so the screen PPI is roughly 91.79. A 2560×1440 monitor at 27 inches works out to about 108.79 PPI, and a 3840×2160 (4K) display at 32 inches to about 137.68 PPI.

Pixel density matters whenever image clarity counts. Designers and photographers use it to check whether a monitor can show fine detail without visible pixel edges; developers use it to reason about CSS pixels, scaling and high-DPI assets; and buyers use it to compare monitors, laptops and phones on a level field. Apple popularised the idea of a “Retina” display — a density high enough that, at a normal viewing distance, the human eye can no longer pick out individual pixels. On phones this is often quoted as roughly 300+ PPI, while laptops and desktops reach the same perceived sharpness at lower numbers because you sit farther away.

As a rough guide, most 24-inch 1080p desktop monitors land near 90 PPI, 27-inch 1440p monitors near 109 PPI, sharp laptops fall between about 120 and 220 PPI, and modern smartphones reach 400–500 PPI. Alongside PPI the tool also reports dot pitch and PPcm. Dot pitch is the distance between the centres of neighbouring pixels in millimetres (25.4 ÷ PPI); smaller is finer, and a 91.79 PPI screen has a dot pitch of about 0.277 mm. PPcm is simply pixels per centimetre (PPI ÷ 2.54) for anyone who prefers metric units.

The aspect ratio — the reduced width-to-height ratio such as 16:9 or 16:10 — and the total pixel count in megapixels round out the picture, making it easy to spot ultrawide, square or unusual panels at a glance.

To use it, type your resolution and screen size, or tap a preset such as 1080p at 24 inches or a modern phone. Results — PPI, dot pitch, pixels per centimetre, aspect ratio, diagonal pixels and total megapixels — update as you type, so you can compare screens side by side in seconds. Everything runs locally, so your numbers never leave your device.

Frequently asked questions

What is a good PPI for a screen?
It depends on viewing distance. Desktop monitors around 90–110 PPI (a 24-inch 1080p panel is 91.79 PPI, a 27-inch 1440p panel 108.79 PPI) look sharp at arm's length. Laptops usually run 120–220 PPI, and phones 400–500 PPI because you hold them closer.
What is the difference between PPI and DPI?
PPI (pixels per inch) describes pixel density on a screen, while DPI (dots per inch) describes ink dots when printing. The two are often used interchangeably, but strictly speaking PPI is the right term for displays and DPI for print output.
How do I calculate my screen's PPI?
Use the formula PPI = √(width² + height²) ÷ diagonal size in inches. For example, a 1920×1080 screen measured at 24 inches has a diagonal of about 2,202.9 pixels, giving 2202.9 ÷ 24 ≈ 91.79 PPI. This calculator does the math for you.
What PPI counts as a Retina display?
Apple's “Retina” marketing means pixels are too small to see at a normal viewing distance, so the threshold depends on distance. On iPhones that is roughly 300+ PPI, MacBook screens are around 220 PPI, and the iMac is about 218 PPI. There is no single fixed number.
Is a higher PPI always better?
Higher PPI gives a sharper image, but only up to the point your eye can resolve at your viewing distance; beyond that you see little difference. Very high densities also demand more GPU power and rely on UI scaling, so the practical sweet spot is around 90–140 PPI for desktops and 300+ PPI for phones.

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