If you have ever printed a photo and seen it come out blurry or pixelated, you have met DPI and PPI. These two acronyms are often used interchangeably, but they mean different things.
DPI: Dots Per Inch
DPI measures how many ink droplets a printer can place in a linear inch. A 300 DPI printer fires 300 drops per inch horizontally and vertically. DPI is a property of the printer.
PPI: Pixels Per Inch
PPI measures the pixel density of a digital image. A 300 PPI image has 300 pixels per inch. PPI is what you control when you export from Photoshop.
The Magic Number: 300 PPI
For professional print, the industry standard is 300 PPI at the final output size.
How Many Pixels Do You Need?
Formula: pixels = (size_in_inches) × (PPI)
For an A4 print at 300 PPI:
- Width: 8.27 × 300 ≈ 2,480 pixels
- Height: 11.69 × 300 ≈ 3,508 pixels
Quick Reference
- Web/screen — 72 PPI
- Draft print — 150 PPI
- Standard print — 300 PPI
- Fine art — 300–600 PPI
- Billboard — 10–30 PPI