CONVERT
FITS → PDF
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Fast, secure FITS to PDF conversion. No registration required.
Setup: FITS is a raster image format with its own balance of compression, colour depth, and software support. Goal: an interchangeable PDF. Our FITS to PDF converter lays your image into a page-sized PDF without re-compressing the pixels when the target format supports that. For JPEG-heavy scans the file size stays comparable; for lossless archival formats the output is larger because the PDF keeps full fidelity. One more beat. FITS is a raster image format with its own balance of compression, colour depth, and software support. Receiving format: PDF is Adobe's Portable Document Format, the fixed-layout standard for shareable documents.
FITS Astronomical Image
Source formatFITS (Flexible Image Transport System) is the standard digital file format in astronomy for storing images, tables, and metadata from telescopes and satellites. It supports multi-dimensional arrays and extensive header metadata for scientific observation records.
PDF Document
Target formatPDF is the universal standard for sharing documents with consistent formatting across all devices and operating systems. It preserves fonts, images, and layout exactly as intended by the author.
Why convert FITS to PDF
PDF is the standard format for receipts, contracts, invoices, signed documents and government filings. Upload systems often reject FITS outright even though it is the same information — converting is the fastest compliance fix.
HOW TO CONVERT
FITS → PDF
Upload the FITS
Drop the image into the uploader. Multiple images produce a multi-page PDF — one page per image.
Compose the page
ImageMagick fits each FITS onto a standard page at the orientation that minimises empty space.
Download the PDF
Receive the composed document; both files auto-delete within the two-hour window.
Common Use Cases
Share across platforms
Send PDF files to anyone without worrying about whether they have the right software for FITS.
Embed in documents
Drop PDF output into Word, Google Docs, PowerPoint, Notion or a website without conversion warnings.
Optimize size
PDF often produces smaller files than FITS for web, email and storage.
Archive & future-proof
Store in a widely-supported format that will still open on future operating systems without legacy plugins.
FITS vs PDF — Strengths and limitations
What each format does best, and where it falls short.
FITS Strengths
- Self-documenting — every file carries complete observational metadata.
- Lossless — bit-exact storage of detector readouts.
- Stable since 1981 with zero breaking changes.
- Mandatory for professional astronomy — every research publication uses it.
- Open standard endorsed by IAU.
Limitations
- Niche — used almost exclusively in astronomy.
- File sizes are large (no default compression).
- Not a display format outside specialized viewers (DS9, AstroBin).
PDF Strengths
- Pixel-perfect fidelity across operating systems, browsers, and printers.
- Embeds fonts, so documents render identically without the reader having them installed.
- Supports digital signatures, encryption, and redaction for legal workflows.
- ISO-standardized (ISO 32000) with multiple validated subsets (PDF/A, PDF/X, PDF/UA).
- Supports both vector and raster content, keeping line art crisp at any zoom level.
Limitations
- Editing is difficult — the format is optimized for display, not mutation.
- Text extraction can scramble reading order in multi-column layouts.
- File sizes balloon quickly when embedding high-resolution images or fonts.
FITS vs PDF — Technical specifications
Side-by-side comparison of the technical details.
FITS
- MIME type
- image/fits
- Extensions
- .fits, .fit, .fts
- Standard
- IAU-endorsed FITS 4.0 (latest revision)
- Header records
- 80-character ASCII cards
- Encoding
- IEEE big-endian integers and floats
- MIME type
- application/pdf
- Current version
- PDF 2.0 (ISO 32000-2:2020)
- Compression
- Flate, LZW, JBIG2, JPEG, JPEG 2000
- Max file size
- ~10 GB (practical); 2^31 bytes (theoretical per object)
- Color models
- RGB, CMYK, Grayscale, Lab, DeviceN, ICC-based
- Standard subsets
- PDF/A, PDF/X, PDF/UA, PDF/E, PDF/VT
| Specification | FITS | |
|---|---|---|
| MIME type | image/fits | application/pdf |
| Extensions | .fits, .fit, .fts | — |
| Standard | IAU-endorsed FITS 4.0 (latest revision) | — |
| Header records | 80-character ASCII cards | — |
| Encoding | IEEE big-endian integers and floats | — |
| Current version | — | PDF 2.0 (ISO 32000-2:2020) |
| Compression | — | Flate, LZW, JBIG2, JPEG, JPEG 2000 |
| Max file size | — | ~10 GB (practical); 2^31 bytes (theoretical per object) |
| Color models | — | RGB, CMYK, Grayscale, Lab, DeviceN, ICC-based |
| Standard subsets | — | PDF/A, PDF/X, PDF/UA, PDF/E, PDF/VT |
FITS vs PDF — Typical file sizes
Approximate file sizes for common scenarios.
FITS
- Backyard-telescope CCD shot (5 MP) 10-30 MB
- Hubble WFC3 single exposure ~65 MB
- JWST NIRCam full detector ~650 MB
- 1-page text-only memo 50–150 KB
- 10-page report with images 500 KB – 2 MB
- Scanned document (per page) 100 KB – 1 MB
- Full-color magazine (48 pages) 10–40 MB
Quality & Compatibility
Pixel data from the FITS travels unchanged when the PDF supports the same encoding (JPEG inside PDF, for example, is stream-copied). When the target requires re-encoding, ImageMagick uses a high-quality default so visible degradation is minimal.
Tips for Best Results
- Orient your FITS correctly before conversion — rotating after the PDF is produced is harder than rotating the image.
- For receipts and documents, enable "auto-crop whitespace" in Advanced so the PDF page is not mostly empty.
- Keep the FITS alongside the PDF; you may need a cleaner re-scan later for higher-quality output.
Frequently Asked Questions
Yes. The free tier accepts files up to 25 MB without registration, email capture or watermarks; paid plans go up to 2 GB. Paid plans raise the size cap, enable batch conversions and provide a REST API for automation, but nothing on the free tier is quality-limited — the output is exactly the same as on any paid plan.
Minimally. When the image encoding carries directly into the PDF (JPEG into PDF for example), pixels are stream-copied and quality is bit-exact. When re-encoding is required, we use high-quality defaults that are visually indistinguishable from the source on typical viewing conditions.
Uploads run over HTTPS, files are processed in isolated containers, and both the source FITS and the PDF output are auto-deleted within two hours. No account is required, file contents are never logged, and KaijuConverter does not use uploads for AI training. The paid plan adds a signable data-processing agreement for regulated workflows.
Yes. Upload multiple images (or a ZIP) and the pipeline produces a multi-page PDF with one image per page, ordered by filename. Advanced options control page size, orientation per page and whether captions are inserted.
Most files finish in well under a minute. Small images and documents are typically ready in a few seconds; large video or audio files scale roughly with duration. Upload speed from your network is usually the dominant factor, not server time.
A4 portrait by default — the global mainstream. Switch to Letter or any custom dimensions in Advanced. You can also select "match image" so the PDF page size tracks the FITS aspect ratio exactly, eliminating white margins for custom printing.
Related comparisons
See these formats side by side to understand which fits your use case best.
Related Guides
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Read guideSecure & Private Conversion
Your files are encrypted during transfer, processed in isolated containers, and automatically deleted within 60 minutes. We never read, share, or store your data.