Screen PPI Calculator

Combine pixel dimensions with physical size

Enter native horizontal and vertical pixels plus the display's physical diagonal in inches. Browser-reported resolution can fill editable pixel fields as a starting point, but physical size must be entered and all values should be verified.

PPI formula

The Pythagorean theorem finds diagonal pixels: square root of horizontal pixels squared plus vertical pixels squared. Divide that diagonal by physical diagonal inches to get pixels per inch. Dividing PPI by 2.54 gives pixels per centimeter.

Worked example

A 1920 × 1080 panel has about 2,202.91 pixels diagonally. Divide by a 24-inch diagonal and density is about 91.79 PPI, or 36.14 pixels per centimeter. A smaller screen with the same resolution has higher density.

Why browser resolution is only a starter

Browsers may report CSS-pixel dimensions affected by scaling, zoom, operating-system settings, remote sessions, privacy protections, or which monitor owns the window. Multiplying by device-pixel ratio can approximate physical pixels, but it is not authoritative and may still describe a different display.

Measure the right diagonal

Use viewable panel diagonal, not device body width or advertised class size rounded to a marketing label. Pixel dimensions should be the panel's native resolution rather than the current lower display mode. Manufacturer specifications are usually better than ruler measurements for both values.

Assumptions and limitations

PPI describes physical pixel density, not effective UI scaling, sharpness, viewing distance, color quality, subpixel layout, print DPI, or whether a person can distinguish individual pixels. Results assume square pixels and a rectangular panel. Browser values never replace entered physical size and remain editable by design.

Screen PPI FAQ

Is PPI the same as CSS pixels?

No. CSS pixels are logical layout units and may be scaled.

Does higher PPI always look better?

No. Content scaling, viewing distance, panel quality, and eyesight also matter.

Can this detect screen inches?

No. Browsers do not reliably expose physical diagonal size.