The math (it's short)
Print size in inches = pixels ÷ DPI. Centimeters = inches × 2.54. A 3000×2000 px photo at 300 DPI prints at 10×6.7 inches (25.4×16.9 cm). Print it bigger and the printer spreads the same pixels thinner — that's when edges go soft.
What DPI do you actually need?
- 300 DPI — anything viewed at arm's length: photo prints, flyers, magazines, business cards.
- 150 DPI — posters and banners viewed from a meter or more away. Totally fine, saves huge files.
- 72–100 DPI — billboards and trade-show backdrops. From across a room, nobody can tell.
Pixels needed for common print sizes (300 DPI)
| Print size | Pixels needed |
|---|---|
| 4×6 in (10×15 cm) | 1200×1800 |
| 5×7 in (13×18 cm) | 1500×2100 |
| 8×10 in (20×25 cm) | 2400×3000 |
| A4 (21×29.7 cm) | 2480×3508 |
| 11×14 in (28×36 cm) | 3300×4200 |
| A3 (29.7×42 cm) | 3508×4961 |
| 16×20 in (41×51 cm) | 4800×6000 |
| 24×36 in poster (at 150 DPI) | 3600×5400 |
FAQ
Does changing the DPI number in Photoshop improve quality?
No — DPI is just an instruction for the printer, not extra detail. Changing 72 to 300 without resampling only changes the intended print size. The pixels are the pixels.
DPI vs PPI — what's the difference?
PPI (pixels per inch) describes digital images; DPI (dots per inch) describes printer ink dots. In everyday design work the terms are used interchangeably, and print shops will understand either.
My image is too small to print — now what?
Either print smaller, drop to 150 DPI if viewing distance allows, or run it through an AI upscaler before sending it to print. Upscalers work shockingly well up to about 2–4×.