PDF compression guides

How to Compare PDF Size Before and After Compression

Use byte counts for the reduction measurement and a separate checklist for document quality.

By PDFStay Editorial Team

Last updated

Compare a PDF before and after compression by recording exact byte size, page count, dimensions, and the features the document needs. Calculate the byte reduction, then inspect the downloaded output for readability, images, links, forms, and searchable text. A percentage is useful for this file pair, but it is not a guaranteed result for another PDF with different content.

Measure bytes consistently

Use the same unit and the same file boundary for both measurements: compare the original PDF with the final downloaded PDF, not a browser preview or compressed archive. PDFStay publishes a benchmark method and JSON records for fixed fixtures, which makes those examples reproducible without turning them into a promise about your document.1, 2

Before-and-after comparison
MetricBeforeAfter
File sizeRecord exact bytesRecord exact bytes
Required featuresList what must workTest the same features

Interpret the percentage with its context

  1. Record original and output bytes and page count.
  2. Calculate reduction from those two exact byte values.
  3. Compare quality and features using the same checklist.
  4. Report the document, mode, and date with any measured percentage.

FAQ

How do I calculate PDF reduction?

Use (original bytes − output bytes) ÷ original bytes × 100. Keep the original and output measurements from the same file pair and unit.

Why did my percentage differ from a benchmark?

Content, images, fonts, page count, and source producer differ. Benchmarks use fixed fixtures and cannot predict every new PDF.

Sources

  1. PDFStay reproducible compression checksPDFStay first-party methodologySource reviewed:
  2. PDFStay compression benchmark data (JSON)PDFStay first-party dataSource reviewed: