Aspect Ratio & PPI Calculator
“Your screen” fills in this display’s native pixel count (CSS size × pixel ratio). Type the physical diagonal from the spec sheet yourself, since no browser can measure it. Nothing leaves your device.
How it works
仕組みEnter a resolution and a diagonal size and this calculator gives you the numbers spec sheets love to omit: the exact aspect ratio as a reduced fraction and a decimal, pixels per inch, dot pitch in millimetres, and total megapixels. Presets cover the common desks (24-inch 1080p, 27-inch 1440p and 4K, and a modern 6.1-inch phone), and the “your screen” button reads this display’s native pixel count straight from your browser, something no static chart can do. Handy for comparing monitors before buying, or for checking whether that tempting panel is actually sharper than the one you have.
The reduced fraction is exact, and many real panels simply aren’t cut to tidy numbers; 2556×1179 reduces to 852:393, for instance. When the fraction looks unwieldy, read the decimal underneath instead: 2.17:1 tells you immediately it is a touch wider than 19.5:9.
Around 90-110 PPI is the classic comfortable range at desk distance: 24-inch 1080p sits near 92 and 27-inch 1440p near 109. A 27-inch 4K panel jumps to about 163 PPI, which looks wonderfully crisp but usually needs OS scaling. Phones held close routinely exceed 400 PPI.
Browsers see the screen in CSS pixels; the button multiplies that by your device pixel ratio to estimate native pixels. On scaled displays the two don’t always multiply back perfectly (a 150% scale factor can round oddly), and some browsers quantise the ratio. Treat it as a very close estimate, not gospel.