Formula
PPI = √(W² + H²) ÷ D
Use Pythagoras to find the diagonal pixel count, convert the physical diagonal to inches, then divide.
Image & screen
● Runs locallyPixel Density / PPI
Calculate geometric pixel density from a screen resolution and measured diagonal. CalcFlow also derives pixel pitch and the physical width and height implied by the same aspect ratio.
Example values
Pixel density
Assumptions
- The diagonal is the active rectangular display area.
- Pixels are treated as square and evenly spaced.
PPI describes pixels per inch. It is related to geometry and does not by itself rate perceived display quality.
Formula review
Formula v1.0.0
Reviewed 2026-08-03
CalcFlow engineering review
Pixel Density / PPI: Worked example
√(3840² + 2160²) ÷ 27 = approximately 163.18 pixels per inch. The corresponding pixel pitch is about 0.1557 mm.
Frequently asked questions
Is PPI the same as resolution?
No. Resolution is the pixel count; PPI combines that count with physical size.
Is PPI the same as print DPI?
Not exactly. PPI describes pixels per inch; printer dot placement is a different physical process.
Does higher PPI always look better?
The calculation does not judge viewing distance, eyesight, panel layout or content quality.