You've scanned a document — a contract, an invoice, an old photo of a certificate — and your scanner or app is asking what format to save it in. BMP, PNG, TIFF, JPG, PDF: the choice affects file size, quality, and how easily you can use the result later. For scanned documents specifically, the right answer is usually different from what you'd pick for a photo or a web graphic. Here's how the three lossless contenders — BMP, PNG, and TIFF — compare, and why for most people PDF is the better destination than any of them.
The three formats, briefly
BMP (Bitmap). The native Windows raster format. Stores every pixel as raw, uncompressed data. Simple, universally readable on Windows, and enormous — a single A4 page scanned at 300 DPI can be 25 MB or more because nothing is compressed.
PNG (Portable Network Graphics). A modern lossless format with efficient compression. Same pixel-perfect quality as BMP but a fraction of the file size, plus full transparency support and universal compatibility across every platform and browser.
TIFF (Tagged Image File Format). The professional scanning standard. Supports lossless compression, multiple colour depths, and — crucially — multiple pages in a single file. The format of choice in legal, medical, and archival document workflows.
How they compare for scanned documents
| Factor | BMP | PNG | TIFF | |---|---|---|---| | Compression | None | Lossless, efficient | Lossless (several methods) | | File size | Very large | Small | Medium | | Multi-page | No | No | Yes | | Transparency | No | Yes | Yes | | Universal support | Windows-centric | Excellent | Specialist software | | Best for | Legacy compatibility | Single-page scans | Professional archives |
File size is the first thing most people notice. BMP is by far the largest because it applies no compression at all. PNG is the smallest of the three for typical scanned documents. TIFF sits in between, depending on which internal compression method it uses.
Multi-page support is where TIFF pulls ahead for documents. A ten-page contract can live in a single TIFF file. BMP and PNG are single-image formats — a ten-page document becomes ten separate files, which is awkward to manage and share.
Compatibility favours PNG. Every browser, phone, and operating system opens PNG instantly. BMP is really a Windows format. TIFF, despite being the professional standard, often won't open in a browser or preview in an email client without specialist software.
Warning
Avoid JPG for scanned documents containing text. JPG uses lossy compression that introduces blurry halos around letters and noise along edges — exactly the kind of detail that matters in a scanned document. JPG is for photographs, not text.
Why PDF usually beats all three
Here's the thing most format comparisons miss: for scanned documents, the best destination is usually not an image format at all. It's PDF. Here's why:
PDF holds multiple pages natively — like TIFF, but with universal support like PNG.
PDF is universally readable — every device on earth opens a PDF without specialist software.
PDF is compressed — far smaller than BMP, comparable to or better than TIFF for scanned content.
PDF is what everyone expects — portals, email recipients, document management systems, and printers all expect PDF. A scanned document in PDF is immediately usable everywhere; a scanned document in BMP or TIFF often needs converting before anyone can use it.
The practical workflow: if your scanner produces BMP or TIFF (many do), convert to PDF for everyday use, archiving, and sharing. Keep the original TIFF only if you have a specific archival requirement that mandates it.
Converting scanned images to PDF without uploading
iSavePDF converts all three formats to PDF entirely in your browser — the scanned document never travels to a server. This matters because scanned documents are so often sensitive: contracts, financial records, ID documents, medical paperwork.
- BMP to PDF — for Windows bitmap scans
- TIFF to PDF — for professional scans, including multi-page TIFFs
Both tools accept multiple files and assemble them into a single PDF. For a multi-page TIFF, each page becomes a PDF page automatically.
Free tool
Convert TIFF to PDF free — files stay in your browser
Convert TIFF scans and archival images into a PDF.
Try TIFF to PDFWhat about going the other way?
If you have a PDF and need individual pages as images — for a presentation, a web upload, or an image editor — PDF to PNG is the best choice for scanned content. PNG's lossless quality preserves the sharpness of scanned text, and the file sizes are manageable. Use PDF to TIFF only if a downstream system specifically requires TIFF.
Note
Scanned BMP and TIFF files are often very large. After converting to PDF, run the result through Compress PDF to reduce the file size for emailing or uploading — the visual quality stays more than good enough for reading and printing.
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