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Screen PPI & Pixel Density Calculator

Find a display's pixels-per-inch, pixel pitch, and simplified aspect ratio from its resolution and diagonal screen size — in inches or centimeters.

Pixel density
233.1 PPI
Pixel pitch
0.109 mm
Aspect ratio
16:9

How it works

The horizontal and vertical pixel counts form a right triangle with the diagonal resolution as the hypotenuse, so by the Pythagorean theorem diagonal pixels = √(width² + height²). Dividing that by the physical diagonal size (converted to inches, the unit PPI is conventionally quoted in) gives pixels per inch: PPI = diagonal pixels ÷ diagonal inches. For a 1920×1080 display measuring 24 inches diagonally, that works out to the commonly-cited ≈91.8 PPI.

Pixel pitch — the physical size of a single pixel, in millimeters — is just the inverse of PPI converted to metric: 25.4 ÷ PPI. The aspect ratio is the same width/height pair reduced to lowest terms using the greatest common divisor (the same reduction `ratio-simplifier` applies to any two numbers), so 1920×1080 reduces to 16:9.

Diagonal screen size is a physical measurement, so it gets this page's metric/imperial toggle — switch to centimeters and the field relabels and rescales, with the result unchanged either way since it's converted to inches internally before the formula runs.

FAQ

What counts as a 'high' PPI?

There's no single fixed cutoff — it depends on viewing distance, since a pixel subtends a smaller angle on your eye the farther away the screen is. A phone held close typically wants a much higher PPI than a TV viewed from across a room to look equally sharp, which is why phones are commonly specced well above 300 PPI while large TVs look sharp at a fraction of that.

Why does my display's marketed resolution not reduce to a 'clean' aspect ratio?

Not every resolution is an exact multiple of a common ratio — for example 1366×768 reduces (via GCD) to 683:384, which isn't a tidy label like 16:9 even though it's visually very close to it. The reduced fraction here is exact math on the pixel counts you entered, not a rounded marketing label.

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