Screen density & dimensions
Monitor PPI calculator.
Find a monitor’s pixel density from its native resolution and viewable diagonal. See PPI, pixel pitch, and estimated physical dimensions together — without assuming your current browser window reveals your exact monitor model.
Enter the resolution from the monitor specifications, not your browser window size. The diagonal must describe the display panel, excluding bezels.
How is PPI calculated?
PPI = √(width pixels² + height pixels²) ÷ diagonal inches. The square root gives the pixel count along the diagonal. Dividing by the physical diagonal gives pixels per inch. If your diagonal is in centimeters, divide it by 2.54 first.
For a 27-inch 2560 × 1440 monitor, the diagonal pixel count is approximately 2,937.21. Divide by 27 to get approximately 108.79 PPI. One pixel is about 25.4 ÷ 108.79 = 0.2335 mm wide.
Monitor pixel density examples
| Display | Native resolution | PPI | Pixel pitch |
|---|---|---|---|
| 24 inches | 1920 × 1080 | 91.79 | 0.2767 mm |
| 27 inches | 2560 × 1440 | 108.79 | 0.2335 mm |
| 27 inches | 3840 × 2160 | 163.18 | 0.1557 mm |
| 32 inches | 3840 × 2160 | 137.68 | 0.1845 mm |
| 34 inches | 3440 × 1440 | 109.68 | 0.2316 mm |
PPI is not the same as browser pixels per inch
Native PPI describes the hardware panel. A web page uses CSS pixels, which can map to multiple hardware pixels because of operating-system scaling and browser zoom. A 27-inch 4K panel is about 163.18 native PPI. At a device-pixel ratio of 1.5, its browser scale can be about 108.79 CSS pixels per physical inch.
Do not paste a native PPI value into an on-screen ruler without accounting for scaling. Our ruler’s screen-diagonal method uses the screen dimensions reported in CSS pixels; card calibration instead matches a known physical reference directly. Verify the result against a trusted ruler when accuracy matters. Read the calibration guide.
What do width and height mean?
The dimensions are calculated from the diagonal and pixel aspect ratio, assuming square pixels and a flat rectangular screen. They describe the viewable panel, not the stand, frame, or desk space needed for the monitor. Manufacturer-rounded diagonals and unusual pixel shapes can introduce differences. For a curved panel, these calculations do not determine the straight-line distance across the curve.
Is higher PPI always better?
Higher density places more pixels in the same physical area, which can improve fine text and image detail. Your experience also depends on viewing distance, software scaling, contrast, panel quality, and the content being displayed. This calculator helps compare density; it does not predict overall monitor quality or recommend a purchase.
PPI versus DPI
PPI means pixels per inch and describes a digital image or display. DPI means dots per inch and commonly describes printing. A printer can use multiple ink dots to render an image pixel, so the two numbers are not directly interchangeable. For a paper measuring scale, download a printable ruler PDF at 100% scale rather than changing its DPI.
Browser scaling reference: MDN: devicePixelRatio. All calculations run locally in your browser.