What Is PPI?
Everything you need to know about pixel density, display sharpness, and why resolution alone isn't enough.
Pixels Per Inch (PPI)
PPI stands for Pixels Per Inch. It is a measurement of the pixel density of a digital display. Essentially, it tells you how many physical pixels are packed into a single square inch of your screen.
While Resolution (like 1920x1080) tells you the total number of pixels, PPI tells you how concentrated those pixels are. This concentration is what determines how "sharp" or "crisp" an image looks to your eyes.
The PPI Calculation
PPI = √(Width² + Height²) / Diagonal Size
Try our PPI Calculator to do this automatically.
Why PPI Matters
Text Clarity
High PPI makes the curves and diagonal lines of fonts look smooth rather than "jagged." This is crucial for reading and coding.
Image Detail
With more pixels per inch, you can see finer details in photos and videos that would be lost on a lower-density screen.
The "Retina" Threshold
There is a point where the human eye can no longer distinguish individual pixels at a normal viewing distance. This is what Apple famously marketed as a "Retina Display."
For a smartphone held about 10-12 inches away, this threshold is around 300 PPI. For a computer monitor at 20-30 inches, the threshold is lower, around 220 PPI.
PPI vs. DPI: The Big Confusion
People often use these terms interchangeably, but they refer to different things:
- PPI (Pixels Per Inch): A digital measurement for screens. Pixels are square light-emitting elements.
- DPI (Dots Per Inch): A physical measurement for printers. Dots refer to individual drops of ink on paper.
If you are a designer, you work in PPI on your screen, but you must ensure your file has enough density (usually 300 "DPI" in software settings) for a high-quality print.