ToolnozaPPI formula for a display
PPI means pixels per inch. For a screen with horizontal resolution W pixels, vertical resolution H pixels and diagonal size D inches: PPI = √(W² + H²) ÷ D. The numerator is the pixel count along the diagonal; dividing by the physical diagonal gives pixels per inch.
For 1920 × 1080 at 24 inches, the diagonal resolution is √(1920² + 1080²) ≈ 2202.9 pixels. Divide by 24: about 91.8 PPI. Use the displayed active-area diagonal, not the bezel-to-bezel measurement.
Why resolution alone is not enough
The same pixel resolution produces a lower pixel density on a larger screen. A 27-inch 1920 × 1080 display therefore has fewer pixels per inch than a 24-inch display at the same resolution. To compare sharpness, keep the resolution and size inputs together; comparing only “1080p” or “4K” misses screen size.
Compare two screens consistently
Calculate each screen using its native resolution and diagonal. A higher PPI means more pixels fit into each linear inch, but perceived sharpness also depends on viewing distance, scaling, panel quality, content and eyesight. A PPI result is a specification comparison, not a guarantee that one screen will look better to every person.
PPI is not print DPI
PPI describes pixels per physical inch on a display. DPI is commonly used for printer dots per inch. The terms are related in some workflows but are not interchangeable descriptions of a monitor. A 300 PPI image printed at a different physical size has a different print resolution; changing the image metadata alone does not add pixels.
Use the PPI calculator
- Enter the screen’s horizontal and vertical pixel resolution.
- Enter its diagonal size in inches or convert centimetres to inches.
- Compare the result with another display at its own native resolution and size.
If you need the visible screen width or height for a desk layout, use the monitor dimensions calculator; PPI answers a different question.