DPI vs PPI: How Many Pixels You Need for a Sharp Print
Pixels needed = print size in inches × PPI. A 6 × 4 inch photo at 300 PPI needs 1800 × 1200 pixels. Everything else is detail.
27 July 2026 · 5 min read · Technology
Print shops ask for "300 DPI", cameras report megapixels and design software talks about PPI. They are related, but they are not the same thing.
DPI and PPI
- PPI (pixels per inch) describes a digital image: how many of its pixels will be spread across each inch when printed.
- DPI (dots per inch) describes a printer: how many ink dots it lays down per inch.
In everyday use, including most print-shop instructions, "300 DPI" really means 300 PPI in your file. The image resolution converter treats them as equal for that reason.
The only formula you need
pixels = inches × PPI
To go from pixels to the largest good print: inches = pixels ÷ PPI.
Common print sizes at 300 PPI
| Print size | Pixels needed | Megapixels |
|---|---|---|
| 6 × 4 in | 1800 × 1200 | 2.2 MP |
| 7 × 5 in | 2100 × 1500 | 3.2 MP |
| 10 × 8 in | 3000 × 2400 | 7.2 MP |
| A4 (8.27 × 11.69 in) | 2480 × 3508 | 8.7 MP |
| A3 (11.69 × 16.54 in) | 3508 × 4961 | 17.4 MP |
How much resolution is enough?
- 300 PPI: photos and small print viewed up close.
- 150–200 PPI: posters viewed from a metre or more.
- 20–50 PPI: billboards viewed from across the road.
Viewing distance matters more than a fixed number.
Metric resolution
Much of Europe specifies resolution per centimetre. Divide by 2.54:
- 300 PPI ≈ 118 pixels per cm
- 150 PPI ≈ 59 pixels per cm
The 72 DPI myth
Screens do not care about the DPI value stored in an image file. A 1920 × 1080 image looks identical on a website whether its metadata says 72 or 300. Only the pixel dimensions matter on screen.
Related conversions
This article is for general information. Please verify figures against the relevant standard before using them in critical work. About accuracy