Screen PPI Calculator
A display PPI calculator for any panel: enter a resolution and the diagonal size from the spec sheet to get the true pixel density, the dot pitch and the physical size of the visible area.
How to use this monitor PPI calculator
Manufacturers quote the diagonal, so the pixel diagonal has to be worked out first: PPI = √(width² + height²) ÷ diagonal in inches. A 27-inch 2560 × 1440 monitor has a 2937 pixel diagonal, giving 108.8 PPI.
Dot pitch is the same information the other way round — the physical distance between pixel centres, usually quoted in millimetres. Divide 25.4 by the PPI to get it.
Worked with the values in the calculator above
PPI = √(2,560² + 1,440²) ÷ 27 in = 108.79 PPI
1 px = 1 ÷ 108.79 PPI = 0.00919 in What pixel density do you need?
Around 110 PPI is comfortable for a desktop monitor at arm’s length. Laptops sit closer, so 140 to 260 PPI is typical. Phones are held closest of all and run from 300 to over 500 PPI.
Your operating system’s scaling setting is a separate matter. A 163 PPI 4K 27-inch monitor is usually run at 150 or 200 per cent scaling, which is why the browser reports a device pixel ratio rather than the real density.
Frequently asked questions
How do I calculate the PPI of my monitor?
Take the square root of width squared plus height squared, then divide by the diagonal in inches. A 24-inch 1920 × 1080 monitor comes out at 91.8 PPI.
What is a good PPI for a monitor?
Around 110 PPI suits a desktop monitor at normal viewing distance. Above 160 PPI text looks noticeably smoother but usually needs display scaling to stay readable.
What is the iPhone pixels per inch figure?
Recent 6.1-inch models are 460 pixels per inch at 1179 × 2556. Older and larger models range from about 326 to 460 PPI.
How do I work out screen pixels per inch?
Combine the two edges into a pixel diagonal, then divide by the diagonal in inches: √(width² + height²) ÷ diagonal.
Is PPI the same as resolution?
No. Two screens can share a 3840 × 2160 resolution and have completely different densities — 163 PPI at 27 inches, 80 PPI at 55 inches.