PNM to FITS Converter
Processing entirely on your device — large files may take a moment.
Portable Anymap and Flexible Image Transport System exist for different jobs: PNM is the umbrella of the netpbm family — P1-P6 auto-detected, covering bitmap, graymap and pixmap in one extension. Tools that say "PNM" accept all of them. Convert FITS frames to PNG or JPG to preview telescope data, or pack them into a ZIP for sharing.
Because the whole conversion happens on your device, it is instant, unlimited and genuinely private — no accounts, no watermarks, no files on anyone's server. Multiple files are converted in one go.
How to convert PNM to FITS
- 1
Select your files
Drag & drop your PNM files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to FITS". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted FITS file individually, or grab everything at once as a ZIP archive.
About the PNM format
PNM is not a format of its own — it is the family name for PBM/PGM/PPM, and files carrying the .pnm extension simply expect the reader to sniff the P1-P6 magic and branch accordingly. It exists because Unix tools always preferred one extension that means "any of these".
This converter auto-detects the member format on input and writes the full-color P6 flavor on output, so a .pnm file turns into anything modern without a separate PBM/PGM/PPM detour.
+Strengths
- ✓One extension for the whole netpbm family
- ✓Auto-detection on both read and write
- ✓Same bulletproof simplicity as PBM/PGM/PPM
!Limitations
- −Ambiguous by design — tools must sniff
- −Inherits all the size downsides of the family
- −Some tools only accept specific members
About the FITS format
FITS (Flexible Image Transport System) has carried professional astronomy data since 1981: every file opens with a plain-text header that records telescope, instrument, exposure, filters and world coordinates, followed by raw pixel arrays — often 16-bit or float, sometimes data cubes.
Values can be negative or far above display range, so FITS never looks right in a photo viewer. Converting to PNG applies a simple scaling pass that reveals the nebula or galaxy in the numbers — good for previews, while science pipelines keep the original.
+Strengths
- ✓Self-documenting science headers
- ✓High bit depth (16/32-bit, float)
- ✓The standard of every observatory
!Limitations
- −Not display-ready
- −Files are large and uncompressed
Why convert PNM to FITS?
There is a concrete reason this conversion exists: Ambiguous by design — tools must sniff FITS sidesteps that — Self-documenting science headers If that is your situation, the tool above settles it in seconds, entirely on your device.
Frequently asked questions
Is this PNM to FITS converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Will I lose quality converting PNM to FITS?
No — FITS is a lossless format, so every pixel of the converted image matches your original PNM file. You can also adjust the quality/size balance before converting when the target format supports compression.
Will transparent areas survive the conversion to FITS?
Transparency is kept whenever FITS actually supports an alpha channel. If the target format has none (like JPG), transparent areas are flattened onto a white background — that is a property of the format, not of this tool.
Can I convert several PNM files at once?
Yes — drop as many files as you like into the tool and they are converted in one batch. When more than one file comes out, everything is bundled into a ZIP for a single download.