DPI vs PPI Explained: The Ultimate Resolution Guide for Web and Print
Demystify DPI (Dots Per Inch) vs PPI (Pixels Per Inch). Understand screen resolution myths, print standards (300 DPI), and calculating physical print sizes.
DPI vs PPI Explained: The Ultimate Resolution Guide for Web and Print
The terms DPI (Dots Per Inch) and PPI (Pixels Per Inch) are frequently used interchangeably in graphic design, photography, and digital marketing, yet they refer to two completely distinct concepts.
1. Defining PPI vs DPI
PPI (Pixels Per Inch) — Digital Displays
PPI refers to the density of digital pixels on an electronic screen (monitors, smartphones, tablets, TV screens).
- An iPhone Retina display has around 460 PPI, meaning there are 460 physical LED/OLED pixels packed into every linear inch of screen space.
- On the web, only total pixel dimensions matter (1920 × 1080). A 1000px image will render identically whether its metadata says 72 PPI or 300 PPI.
DPI (Dots Per Inch) — Physical Printers
DPI refers to the physical density of ink dots emitted by a printing press or inkjet printer onto paper.
- A professional printer uses multiple micro-dots of cyan, magenta, yellow, and black ink to reproduce a single image pixel.
- 300 DPI is the gold standard for crisp, photographic-quality physical prints.
2. The Famous "72 DPI Web Myth"
For decades, designers claimed that images for the web must be saved at "72 DPI". In reality:
- Web browsers ignore DPI/PPI metadata tags entirely.
- A 1200 × 800 pixel image saved at 72 DPI and the same image saved at 300 DPI contain the exact same number of pixels and render identically on every screen.
3. How to Calculate Dimensions for 300 DPI Print
To calculate the required pixel resolution for any physical print size:
$\text{Required Pixels} = \text{Print Size (Inches)} × \text{Desired DPI}$
| Print Size | In Inches | Required Pixels @ 300 DPI |
|---|---|---|
| Standard Photo (4x6) | 4'' × 6'' | 1200 × 1800 pixels |
| Medium Photo (8x10) | 8'' × 10'' | 2400 × 3000 pixels |
| A4 Document | 8.27'' × 11.69'' | 2480 × 3508 pixels |
| A3 Poster | 11.69'' × 16.54'' | 3508 × 4960 pixels |