PPI calculator
Screen pixel density from the resolution and the diagonal.
Fill in the fields and the result will appear here automatically.
Calculate geometric pixel density of the active display from resolution and diagonal in inches. For a rectangular screen with square pixels, the grid diagonal follows Pythagoras. The result also shows one-pixel pitch in millimetres. These figures alone do not determine text readability or invisible pixels.
How it works
Formula and logic
Pixel-grid diagonal Dpx=√(W²+H²). Density PPI=Dpx/Din and pixel pitch in mm=25.4/PPI. W and H are positive safe integers; diagonal in inches is a positive finite number. The model assumes square pixels and the active rectangular area. Printer DPI cannot be determined from these inputs.
Example
A 1920×1080 screen with a 15.6-inch diagonal has a density of 141.21 ppi.
Fields and units
- Horizontal resolution — px
- Vertical resolution — px
- Diagonal — in
How to use
- — Enter the screen resolution in pixels.
- — Give the diagonal in inches.
- — Read the pixel density and the size of one pixel.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- Square-pixel geometry of the active display area. Vision, readability, subpixel structure and print quality are not assessed.
FAQ
How does PPI differ from DPI?
The arithmetic is the same, but PPI describes screen pixels and DPI printed dots. A printer dot and a monitor pixel work differently, so one figure cannot be carried over to the other.
Why does the same resolution look different?
At the same 1920×1080 resolution, 15.6″ gives about 141.21ppi and 40″ gives 55.07ppi. Physical pixel pitch differs; perceived detail also depends on distance, vision and content.
What density is enough?
It depends on viewing distance: a phone is held close and needs more, a television is watched from afar and needs less. There is no universal threshold.
What does the pixel size show?
The side of one pixel in millimetres. It is a handy way to judge whether a thin line or small type will be legible.