Understanding DPI vs PPI: What's the Difference?
April 11, 2026 · ScreenRes.tools
DPI (dots per inch) and PPI (pixels per inch) are two of the most confused terms in display technology. While they both describe density, they apply to entirely different contexts.
PPI — Pixels Per Inch
PPI measures the pixel density of a screen. It tells you how many physical pixels are packed into one inch of your display. A higher PPI means sharper text and images.
For example, a 27-inch 4K monitor (3840 × 2160) has roughly 163 PPI, while a 27-inch 1080p monitor only reaches about 82 PPI — making text noticeably less crisp.
How PPI is calculated
PPI = √(width² + height²) / diagonal_inches
You can check your display's PPI using our DPI Checker tool.
DPI — Dots Per Inch
DPI is a printing term. It measures how many ink dots a printer places in one inch. A 300 DPI print is considered high quality for most documents, while photo prints often use 600 DPI or higher.
Why the confusion?
Operating systems like Windows use "DPI" to refer to display scaling settings, even though they're technically controlling how CSS pixels map to device pixels. This is actually a DPR (Device Pixel Ratio) concept, not true DPI.
When does it matter?
| Scenario | Use |
|---|---|
| Buying a monitor | PPI — higher is sharper |
| Printing a photo | DPI — 300+ for quality |
| Web development | DPR — controls scaling |
| UI design | PPI — determines asset sizes |
Key takeaway
- PPI = screen sharpness
- DPI = print quality
- DPR = scaling factor between CSS and device pixels
Understanding these distinctions helps you make better decisions about display purchases, design workflows, and print output quality.