Estimate a PDF's compression gain

Before running an actual compression, quickly find out if it's worth it: this tool analyzes your PDF and gives a rough estimate of the expected size reduction.

Drag and drop your PDF here, or click to select it (100 MB max).

How it works

The tool examines the number of pages, the number and total weight of the images embedded in the PDF, and the proportion of these images already compressed as JPEG. A document consisting mostly of already-compressed images offers little room for improvement; a document with many uncompressed images (raw bitmaps, PNG reinserted without compression) has high potential. A document with few or no images (mostly text) has a more modest gain, coming mainly from optimizing the PDF's internal streams.

Is this estimate accurate?

No, it's deliberately a rough estimate based on simple heuristic tiers (for example "10 to 20%" or "50 to 70%" depending on the proportion of already-compressed images), not an actual compression trial. The real result after an effective compression may be quite different. The goal is simply to give you a quick idea before running the process.

What should I do if the estimated gain is low?

If the estimate shows a low gain (around 10 to 20%), this is generally a sign that the document is already optimized: further compression probably won't help much and might even degrade image quality for a minimal size gain. A high estimated gain, on the other hand, justifies running an actual compression.

As with all our PDF tools, this analysis is calculated 100% locally in your browser thanks to WebAssembly: your document never leaves your device.