Convert J2K to FITS

Why upload sensitive J2K files to online converters? reaConverter processes everything locally — convert to FITS with zero cloud risk.

J2K to FITS conversion is faster with the right tool. reaConverter handles everything from a few files to thousands in one batch. Processes files consistently every time, with full control over quality and output settings.

1. Download and Install reaConverter

reaConverter is a standalone Windows app — download, install, and start converting J2K files in under two minutes. Built-in editing tools let you resize, crop, or watermark as you convert.

Install reaConverter

2. Load your J2K files

Open reaConverter and import your .j2k files. No file limits, no slowdowns. Add as many as you need.

Drag files into the window, use the Add Files button, or select entire folders.

3. Select FITS as output format

Select FITS as target format and pick where to save results. You can keep default settings or fine-tune the output.

4. Start J2K to FITS conversion

Hit Convert to process your files. The log window shows progress, timing, and status for every file.

Conversion complete? Your FITS files are saved to the destination folder, ready to use.

J2K to FITS Converter

reaConverter offers the fastest, simplest solution for converting your J2K files into FITS in seconds - all images processed on your PC for maximum privacy and speed.

Download Free Trial

Do more with your images

Converting J2K images for use in a larger project? With reaConverter, you can convert, edit, and enhance your images in one streamlined process.

Our range of editing options includes such image processing actions as Resize, Rotate, Crop, Color Replace, Watermarks and more. Adjust actions include RGB, HLS, HSV, Brightness and Contrast. Auto-processing options are also available, such as auto-rotate and auto-crop.

Image editing tools

User Reviews

Average User Rating:
Last updated on January 20, 2026

"Essential for our astroimaging pipeline! reaConverter perfectly handles FITS files from our research telescope, preserving all WCS coordinates and photometric data during batch conversion to TIFF. Now we process 100+ deep-sky exposures nightly without losing critical metadata for our exoplanet studies!"

Joseph Wilson

Satisfied Customer

"reaConverter makes FITS conversion incredibly easy. We batch convert astronomical images to standard formats for presentations and analysis, all automated through the command-line. It’s fast, reliable, and handles large datasets without issues."

Laura N.

Astrophysics Research Assistant

"Finally an app that actually opens my weird files! Saves me from format frustration daily."

Kyle Brooks

Happy User

"This converter delivers exceptionally quick format conversions with reliable results every time."

Brian White

Happy User

"Security was our top concern when evaluating file conversion tools. reaConverter’s offline mode and role-based access controls let us lock it down for sensitive environments. No unexpected network calls or bloat — just clean, fast conversions. Even passed our pen-testing scans without a hitch."

Marcus White

Healthcare IT

"Your solution was buried deeper in search results than it should be. After struggling with unclear alternatives, I found your guides — finally, instructions that made sense for a first-time user like me. Excellent work!"

Richard E. Miller

Satisfied Customer

J2K to FITS Conversion: FAQ

Can reaConverter convert J2K to FITS?

Yes! reaConverter instantly converts .j2k to .fits with perfect quality preservation. With its batch processing feature, you can convert multiple files at once in just a few clicks. You can even convert images directly from Windows Explorer using the right-click menu — fast and convenient.

What is reaConverter used for?

reaConverter is a software program used for converting images and other types of files from one format to another. It supports a wide range of file formats and allows users to convert multiple files at once, making it a valuable tool for graphic designers, photographers, and other professionals who work with digital images. reaConverter also includes features for resizing, cropping, and editing images, along with batch processing capabilities that help automate repetitive tasks.

Can I convert J2K to FITS online?

If you only need to convert a few J2K files to FITS format, feel free to try our free online free online J2K to FITS converter — perfect for small batches with no installation needed!

How can I turn J2K files into FITS on my computer?

The best way to change J2Ks to FITSs on your PC is to install a quality piece of software, such as reaConverter. This software is extremely efficient in managing a wide range of batch files conversions, including conversion from J2K to FITS.

How can I automate J2K to FITS files conversion?

reaConverter supports all the most useful automation features such as right-click сonversion and Watch Folders for the most efficient automated files conversion in any software of this type.

Is there a way to convert J2K files to FITS using the command prompt?

reaConverter provides full access to all its features via Windows command line, including a high-performance command-line j2k to fits converter for batch processing.

What else can I do with reaConverter?

Convert vector files Convert picture color space Convert Gerber files Crop picture Convert GIS files