Pixel Density Calculator

Resolution Alone Doesn't Tell You How Sharp a Screen Looks

Two screens can share the exact same resolution and look completely different in sharpness, because pixel density depends on how tightly those pixels are packed into a physical area. A 1920×1080 image spread across a 55-inch TV is comfortably sharp at a normal viewing distance; the same 1920×1080 packed into a 13-inch laptop panel produces a visibly crisper, higher-PPI image. This calculator computes the pixels-per-inch figure that actually determines perceived sharpness.

The Formula

PPI comes from the diagonal pixel count divided by the physical diagonal size:

Diagonal (px) = √(Width² + Height²)
PPI = Diagonal (px) / Diagonal (in)

If the screen size is given in centimeters, it's converted to inches (dividing by 2.54) before the PPI division, since pixel density is conventionally expressed as pixels per inch.

Where Pixel Density Matters

Comparing displays while shopping — two monitors with the same resolution but different physical sizes will look meaningfully different in sharpness, and PPI quantifies that difference.
UI and font scaling — operating systems use PPI (or the related DPI) to decide how large to render text and icons so they stay a consistent physical size across displays.
Print and photo work — assessing whether an image has enough resolution to look sharp at its intended output size, whether on-screen or printed.
"Retina"-class marketing claims — verifying a manufacturer's sharpness claim against the actual computed PPI rather than taking the label at face value.

Typical Pixel Density by Device Category

Computed PPI for representative resolution/size combinations
Device Type	Resolution	Diagonal	PPI
Desktop monitor	1920 x 1080	24 in	91.8
Desktop monitor	2560 x 1440	27 in	108.8
Laptop	1920 x 1080	13.3 in	165.6
Smartphone	2556 x 1179	6.1 in	461.4

Smartphones pack far more pixels per inch than monitors because they're viewed much closer to the eye — a lower PPI is perfectly sharp at arm's length, but looks coarse a few inches from your face.

How to Use This Calculator

Enter Horizontal Resolution (px) and Vertical Resolution (px).
Enter the screen's Diagonal Screen Size and choose Inches or Centimeters.
Select Calculate to get the PPI figure along with the total pixel count.

Related Calculations

Need to size a screen from a target PPI instead? Use the Screen Size Calculator. Comparing monitors specifically? See the Monitor PPI Calculator.