What is DPI?
DPI stands for Dots Per Inch. It is a measure of physical print resolution — specifically, the number of ink dots a printer places within one linear inch of paper. The more dots, the finer the detail on the page.
What is PPI?
PPI stands for Pixels Per Inch. It is the screen equivalent of DPI — measuring how many pixels are packed into one inch of a display. This is what determines how sharp an image looks on your phone or laptop. Understanding PPI is essential for improving website speed.
DPI vs PPI Comparison
| Feature | DPI (Dots) | PPI (Pixels) |
|---|---|---|
| Medium | Physical Print | Digital Screens |
| Standard | 300 DPI | Varies by Device |
| Key Goal | Fine detail on paper | Clarity on displays |
The 72 DPI Myth
For decades, designers were told "web images must be 72 DPI." This is a myth.
Modern browsers ignore the DPI metadata inside an image file. A 1000px wide image will take up the same amount of space regardless of whether it's set to 72 DPI or 3000 DPI. What actually matters is the aspect ratio and pixel dimensions.
DPI Standards for Print
If you are sending something to a professional printer, you need these numbers:
- 300 DPI: Business cards, brochures, and photos you hold in your hand.
- 150 DPI: Posters and large banners viewed from a few feet away.
- 72-100 DPI: Billboards viewed from across the highway.
If your image is low-resolution, use an image resizer to check your final print dimensions before continuing.
Conclusion
In short: If it's for a screen, focus on Pixels and optimization. If it's for a printer, focus on DPI. Knowing the difference ensures your work looks crisp in both the physical and digital worlds.