The quality of the source PDF determines much of the final result. Start with a sharp original, especially for scanned text or diagrams. If the images will be viewed at a large size, inspect the downloaded JPGs before publishing or printing them.
Understanding DPI and resolution
DPI (dots per inch) describes how many pixels are used to represent one inch of the original document. Higher DPI means more detail, but also larger file sizes. For screen viewing, 150 DPI is often sufficient. For print, 300 DPI is the standard.
When converting PDF to JPG, the converter renders each page at a specific resolution. This resolution determines the dimensions of the output image in pixels. A typical A4 page at 150 DPI produces an image around 1240×1754 pixels. At 300 DPI, the same page would be roughly 2480×3508 pixels.
When 150 DPI is enough
For sharing on screens, messaging apps, or embedding in presentations, 150 DPI usually provides a good balance between clarity and file size. Most monitors display content at 72–150 DPI equivalent, so higher resolutions offer diminishing returns for on-screen viewing.
If you are preparing images for a website, email, or social media, 150 DPI (or even lower) is typically appropriate. The resulting JPEG files will load faster and take less storage space.
When to prefer 300 DPI
For printing, detailed diagrams, or archival purposes, 300 DPI preserves more detail and reduces visible compression. If the images will be viewed at close range or enlarged, the extra resolution helps maintain sharpness.
Professional printing often requires 300 DPI at the final print size. If you plan to print the converted images, starting with a high-resolution source PDF and converting at 300 DPI will give the best results.
Practical tips
- Start with the highest quality source PDF available.
- For screen sharing, 150 DPI is a good default.
- For print or archival, use 300 DPI.
- Always review the output before distributing or printing.