Pixel Density Calculator
Calculate the pixel density (PPI) of any screen from its resolution and diagonal size. Enter the horizontal and vertical pixels (like 2560 × 1440) and the diagonal in inches (like 27) to get the exact pixels per inch, the dot pitch in millimeters, the aspect ratio, and the total megapixels. PPI tells you how sharp a display will look — perfect for comparing monitors, laptops, phones, and TVs, checking if a screen is 'Retina-class', and judging detail at your viewing distance.
The diagonal is the corner-to-corner size manufacturers advertise.
ToolsSoup's Pixel Density Calculator turns a screen's resolution and diagonal size into the number that actually tells you how sharp it will look: pixels per inch (PPI). Enter the horizontal and vertical pixel counts — say 2560 × 1440 — and the diagonal in inches, like 27, and instantly read the PPI, the dot pitch in millimeters, the simplified aspect ratio, and the total megapixels. A higher PPI means finer detail and smoother text, so this is the fastest way to compare monitors, laptops, phones, and TVs, decide whether a display is 'Retina-class', and understand what a spec sheet really means for image quality. Everything runs in your browser: no uploads, no sign-up, and your numbers never leave your device.
What is a pixel density calculator?
A pixel density calculator works out how many pixels are packed into each inch of a screen — its PPI (pixels per inch) — from two numbers you can find on any spec sheet: the resolution and the diagonal size. The resolution tells you how many pixels the display has (for example 1920 × 1080), and the diagonal tells you how physically large it is. On their own neither number describes sharpness, because the same resolution looks crisp on a phone and coarse on a TV. By combining them, the calculator reveals the real pixel density, which is what determines how detailed and smooth the image appears.
How to calculate pixel density
You only need three numbers, and the results update as you type:
- Enter the horizontal pixel count (the first number in a resolution like 2560 × 1440).
- Enter the vertical pixel count (the second number).
- Enter the diagonal size of the screen in inches.
- Read the PPI, dot pitch, aspect ratio, and total megapixels in the result panel.
- Or click a preset like 27" 1440p to load a common display instantly.
The PPI formula
Pixel density is the number of pixels along the screen's diagonal divided by the diagonal length in inches. To get the diagonal pixel count, take the square root of (horizontal pixels² + vertical pixels²) — the Pythagorean theorem. Then divide by the diagonal size. For a 27-inch 2560 × 1440 monitor, the diagonal pixel count is about 2937, and dividing by 27 gives roughly 109 PPI. A 24-inch 1920 × 1080 screen works out to about 92 PPI, while a modern phone can exceed 400 PPI on a much smaller panel.
What is dot pitch, and how does it relate to PPI?
Dot pitch is the distance between the centers of two neighbouring pixels, usually measured in millimeters — and it's simply the inverse of pixel density. Convert by dividing 25.4 (millimeters per inch) by the PPI. A higher PPI means a smaller dot pitch and finer detail, while a low PPI means a larger dot pitch and visible pixels up close. A 109 PPI monitor has a dot pitch of about 0.233 mm. Dot pitch is the spec older displays advertised before PPI became common, so this calculator reports both.
Why use this pixel density calculator?
- Converts any resolution and diagonal into exact pixels per inch (PPI).
- Also reports dot pitch in millimeters, the simplified aspect ratio, and total megapixels.
- Tells you whether a display is low, standard, high, or Retina-class density.
- Includes presets for popular monitors, laptops, phones, and TVs and updates live as you type.
- Runs entirely in your browser — free, no ads, and your numbers never leave your device.
Frequently asked questions
How do I calculate the pixel density of a screen?
Divide the diagonal pixel count by the diagonal size in inches. The diagonal pixel count is the square root of (horizontal pixels² + vertical pixels²). This calculator does it for you — just enter the resolution and the diagonal and it returns the PPI instantly.
What is a good PPI for a monitor?
For a desktop monitor viewed at arm's length, anything from about 90 to 110 PPI looks fine, and 140 PPI or more (such as a 27-inch 4K display) looks noticeably sharper. Phones and tablets are held closer, so they need much higher densities — often 300 PPI or more — to look equally crisp.
What counts as a Retina display?
Apple coined 'Retina' to mean a display whose pixels are too small to distinguish at a normal viewing distance. There's no single PPI threshold because it depends on distance, but as a rough guide phones above roughly 300 PPI and laptops or monitors above about 220 PPI are usually considered Retina-class. This tool flags screens in that range.
What is the difference between PPI and dot pitch?
They describe the same thing from opposite directions. PPI counts how many pixels fit in an inch, while dot pitch measures the distance between neighbouring pixels in millimeters. Divide 25.4 by the PPI to get the dot pitch, so a higher PPI always means a smaller dot pitch and finer detail.
Does higher pixel density always look better?
Higher PPI gives sharper text and smoother edges, but only up to the point your eyes can resolve at your viewing distance. Beyond that, extra density makes little visible difference and mainly increases the GPU and battery load needed to drive all those pixels. The right density depends on how close you sit to the screen.