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 — and understanding them saves a lot of frustration.
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 300 vertically — that is 90,000 drops per square inch. Most home inkjet printers run between 300 and 1,200 DPI. DPI is a property of the printer, not the image.
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 or resize in your editor. To print at a given physical size, the image must have enough pixels to fill the target area at a sufficient PPI.
The Magic Number: 300 PPI
For professional-quality print, the industry standard is 300 PPI at the final output size. This is the point where the human eye, viewing a print at normal reading distance, cannot distinguish individual pixels.
How Many Pixels Do You Need?
The formula is simple:
pixels = (size_in_inches) × (PPI)
So for an A4 print (8.27 × 11.69 inches) at 300 PPI:
- Width: 8.27 × 300 ≈ 2,480 pixels
- Height: 11.69 × 300 ≈ 3,508 pixels
PPI for Screen vs Print
- Print — 300 PPI (high quality), 150 PPI (acceptable), 72 PPI (screen-only)
- Screen — 72 PPI or 96 PPI traditional; modern displays (Retina, 4K) effectively 200+ PPI
- Web — pixel dimensions matter, not PPI
Quick Reference
- Web/screen — 72 PPI
- Draft print — 150 PPI
- Standard print — 300 PPI
- Fine art / photo — 300–600 PPI
- Billboard — 10–30 PPI (viewed from far away)