1. DPI vs. PPI: The Definitions
People often use the terms DPI (Dots Per Inch) and PPI (Pixels Per Inch) interchangeably, but they refer to different things:
- PPI refers to the number of digital pixels displayed per inch on a screen. It determines digital image resolution.
- DPI refers to the number of physical ink dots sprayed per inch on a printed page. It determines print quality.
When rasterizing vector PDFs, the rendering scale determines the output image's resolution, mapping vector coordinates to a grid of pixels.
2. How Rendering Scale Maps to DPI
Our PDF converter uses rendering scales to generate different resolutions:
- Scale 1.0 (72 DPI): Maps one PDF point directly to one pixel. Great for quick, lightweight web previews.
- Scale 1.5 (150 DPI): Provides standard quality for screens. Good for reading text.
- Scale 2.0 (300 DPI): Standard high-quality print resolution. Renders sharp text and images.
- Scale 3.0 (450 DPI): High-fidelity resolution. Ideal for large prints or detailed diagrams.
⚠️ Memory Tip
Higher rendering scales increase browser memory usage. For large PDFs, process pages in batches to prevent browser slowdowns.
3. Managing Browser Memory
Because the PDF conversion runs inside your browser tab, your device's memory limits how many pages you can render at once. To prevent issues, our tool converts pages sequentially. For documents over 50 pages, we recommend converting page ranges in chunks.
4. Quality vs Size Matrix
| Scale | DPI Equivalent | Quality Level | File Size (Approx) |
|---|---|---|---|
| 1.0 | 72 DPI | Web Preview | 150KB - 300KB |
| 1.5 | 150 DPI | Standard Screen | 400KB - 700KB |
| 2.0 | 300 DPI | Print Ready | 1MB - 2.5MB |
| 3.0 | 450 DPI | Ultra Sharp | 3MB - 6MB |
