Most PDF-to-JPG converters ask you to choose a 'scale' or 'DPI' before starting. This setting determines both the sharpness of your text and the final file size. Set it too low, and your text turns blurry; set it too high, and you get a massive, bloated file. Understanding these numbers helps you choose the perfect setting every time.
Understanding 'Scale' vs. 'DPI'
Unlike images, PDF files are vector-based documents composed of mathematical paths and fonts—meaning they have no fixed resolution. To convert them into images, the converter must map the page onto a pixel grid. The scale tells it how large to draw that grid. A 2x scale doubles both the width and height of the original page (quadrupling the total pixel count). A denser grid results in smoother curves and sharper text edges.
Converters often measure this in DPI (dots per inch). As a rule of thumb, use 72 DPI for basic screen viewing, 150 DPI for standard web use or light printing, and 300 DPI for high-quality, crisp prints.
Screen vs. Print Benchmarks
Select your scale based on how you plan to use the final image:
- Standard web & screen use: A 1.5x to 2x scale (approx. 110–150 DPI) works perfectly.
- Presentations & high-res screens: Opt for 2x to 3x scale to prevent blurriness when zooming.
- High-quality printing: You need a 300 DPI equivalent scale (roughly 4x). Lower settings will result in jagged, pixelated text when printed.
Measured: pixel size and file size by scale
Raising the scale buys sharpness and costs bytes. We rasterized one A4 page at several resolutions and read the actual file sizes.
| Resolution | Scale | Pixel size | JPG | PNG |
|---|---|---|---|---|
| 72 DPI | 1x | 595x842 | 39 KB | 10 KB |
| 150 DPI | 2.08x | 1241x1754 | 105 KB | 26 KB |
| 300 DPI | 4.17x | 2481x3507 | 240 KB | 66 KB |
For text-heavy documents PNG comes out smaller than JPG. At 300 DPI it is 240 KB as JPG against 66 KB as PNG, making PNG 72% lighter, and sharper as well. Lossless compression is simply more efficient on pages built from few colors, such as black text on white. For pages dominated by photographs the ranking flips.
Balancing Sharpness and File Size
While higher scales sharpen text, file sizes increase exponentially with pixel count. Stepping up from 2x to 4x quadruples the total pixels, leading to a much larger file. Instead of automatically choosing the maximum resolution, consider how the image will be viewed. If users are only reading the document on a standard screen, a 2x scale delivers crisp legibility while keeping the file lightweight.
Additionally, JPG compression can introduce noise or 'artifacts' around the sharp edges of text and gridlines. A slightly higher scale helps dilute this noise, making it less visible.
When to choose PNG over JPG
If your PDF consists of photos, JPG offers the best compression-to-quality ratio. However, for documents packed with text, lines, tables, or sharp screenshots, PNG is the superior choice. As a lossless format, PNG keeps fine text crisp without smearing. Plus, if the document page is mostly solid white, PNG files remain surprisingly lightweight.
To sum up: choose your target size first, aim for 2x scale for screen viewing or 300 DPI for print, and choose PNG for text-heavy layouts. Switching's PDF-to-JPG and PDF-to-PNG converters process documents entirely inside your browser. Because we never upload your files to a server, you can safely convert sensitive PDFs like contracts, financial records, or transcripts at your desired resolution.