PPI Calculator — Screen Pixel Density & Dot Pitch
Calculate a display’s pixels per inch, dot pitch and megapixels from its resolution and diagonal size, with common monitor comparisons.
🔒 Runs entirely in your browser. Your input and output are never sent to a server or stored — fully private.
For comparison
PPI = √(width² + height²) ÷ diagonal. Higher PPI means finer detail; beyond ~110 PPI at desktop viewing distance you may want OS scaling.
About this tool
Enter a screen's resolution and diagonal size, and this calculator returns its pixel density in PPI (pixels per inch), the dot pitch in millimeters, and the total megapixel count. It is a quick way to compare monitors, laptops, phones and TVs on an equal footing — a 27-inch 4K display and a 6-inch phone can have wildly different sharpness at the same resolution. Handy when shopping for a display or choosing a scaling factor. Everything is calculated locally in your browser, with nothing sent to any server.
Frequently asked questions
How is PPI calculated?
PPI is the diagonal resolution in pixels divided by the diagonal size in inches. First the diagonal pixel count is found with the Pythagorean theorem — the square root of width² plus height² — then divided by the screen's diagonal. For a 27-inch 4K monitor: √(3840² + 2160²) ≈ 4406 pixels, and 4406 ÷ 27 ≈ 163 PPI. Dot pitch is simply the inverse, converted to millimeters: 25.4 ÷ PPI.
Is a higher PPI always better?
Not necessarily — viewing distance is the other half of the equation. A phone held 30 cm from your eyes benefits from 400+ PPI, while a desktop monitor at arm's length looks sharp around 110–160 PPI, and a TV across the room needs far less. Beyond the point where your eye can no longer resolve individual pixels, extra density adds no visible sharpness but still costs GPU performance, battery life and money.
What is dot pitch, and is my input kept private?
Dot pitch is the distance between the centers of two adjacent pixels, measured in millimeters — the physical size of a single pixel, in effect. Smaller is sharper: 0.25 mm is typical for a modern desktop monitor, while high-density phone screens go below 0.06 mm. As for privacy, every figure is computed by JavaScript running locally in your browser; the resolutions and sizes you enter are never uploaded or stored on a server.