BMP to FITS Converter
Processing entirely on your device — large files may take a moment.
BMP is Windows’ native uncompressed bitmap format. Every pixel is stored exactly as captured, which makes files large but trivially simple to read — common in older software and scanners. 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 BMP compares to FITS
| BMP | FITS | |
|---|---|---|
| Compression | Usually none (RLE optional) | None (optionally Rice/GZIP) |
| Transparency | Rarely (V5 header only) | Not supported |
| Animation | Not supported | Not supported |
| Metadata | Minimal | Rich text header (WCS) |
| Best for | Legacy software and scanner output | Telescope frames, science data |
How to convert BMP to FITS
- 1
Select your files
Drag & drop your BMP 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 BMP format
BMP is Windows' native bitmap format, dating to 1990. It stores pixels essentially raw — rows of BGR values padded to 4-byte boundaries — with optional RLE compression that almost nobody uses. That simplicity is its whole personality: any program written since the dawn of Windows can read one in a dozen lines of code, which is why scanners and ancient lab software still emit it.
The cost of that simplicity is size: an uncompressed BMP of a photo runs dozens of times larger than a JPG. There is no meaningful metadata standard, transparency only exists via the rarely-implemented V5 header, and no modern workflow needs it. Treat BMP as a legacy interchange format you convert away from.
+Strengths
- ✓Zero compression artifacts — pixels stored as captured
- ✓Trivially easy to decode, even in ancient software
- ✓Universal inside the Windows world
!Limitations
- −Enormous files — dozens of times larger than JPG
- −No real metadata or color-management story
- −No role in modern web or print workflows
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 BMP to FITS?
There is a concrete reason this conversion exists: Enormous files — dozens of times larger than JPG 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 BMP 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 BMP to FITS?
No — FITS is a lossless format, so every pixel of the converted image matches your original BMP 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 BMP 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.