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PDF scan size calculator
Estimate how large a scanned PDF may be before capturing a long packet. Adjust the page count, paper size, resolution, color mode, and compression profile to compare practical storage and sharing choices.
What it does
A fast planning estimate
This calculator estimates compressed image-based PDF size from page dimensions and pixel density. It is useful for deciding whether 150, 300, or 600 DPI and grayscale or color are reasonable for a document. Actual results vary because scanner cleanup, blank areas, image complexity, OCR text layers, and PDF encoders compress differently.
Interactive tool
PDF scan size calculator
Inputs stay in this page. The calculator does not upload a document, image, script, or result.
How the PDF size estimate works
The calculator converts the selected paper dimensions into pixels using the chosen dots per inch, then applies a planning factor for black-and-white, grayscale, or color compression. It adds a small allowance for PDF structure and an OCR text layer. This is intentionally a range rather than a single guaranteed number because a blank form compresses far more efficiently than a colorful magazine page.
No page is uploaded or analyzed. The tool cannot see photographs, handwriting, shadows, or blank margins, so it cannot predict the exact encoder result. Use the range to compare settings. For an exact answer, scan three representative pages with the intended app, divide the resulting file size by three, and multiply by the final page count.
Which DPI should a document scan use?
150 DPI can be sufficient for a screen-only reference with large printed text, but it leaves less detail for OCR and later zooming. 300 DPI is a common practical balance for receipts, forms, notes, and ordinary printed pages. 600 DPI creates four times as many pixels as 300 DPI and is better reserved for tiny print, line art, fragile originals, or material that will be cropped heavily.
More resolution does not repair motion blur, glare, poor focus, or a curved page. Capture quality should be improved before increasing DPI. A sharp 300 DPI page can be more useful and smaller than a badly lit 600 DPI page.
Color, grayscale, or black and white?
Black-and-white compression is efficient for clean printed text and high-contrast forms. Grayscale preserves pencil marks, stamps, shading, and weak receipt text without carrying full color. Color is appropriate when ink color, highlights, photographs, signatures, diagrams, or the physical appearance of the original has meaning.
Do not remove color solely to reduce size when the color is evidence. For formal records, follow the document owner’s policy. When the goal is sharing rather than archiving, keep a higher-quality source and create a smaller derivative instead of repeatedly recompressing the only copy.
How to reduce a scanned PDF safely
- Crop unnecessary background and remove accidental or blank pages.
- Use 300 DPI unless smaller detail genuinely requires 600 DPI.
- Choose grayscale for text documents that do not need color evidence.
- Test OCR and legibility after compression, not only the file size.
- Keep an original when retention, audit, or legal requirements apply.
FreeScanner can capture or import multipage documents, correct and reorder pages, create searchable PDFs, and support additional PDF organization. The estimate here helps choose inputs; the exported result remains the only reliable measurement.