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FIT FITS
File conversion

Convert FIT to FITS

Verified by Adam B.· reviewed by FE Editorial ·updated Sep 5, 2026
QUICK ANSWER
Is it possible to convert FIT to FITS?
Yes - FIT converts to FITS.

Rename image.fit to image.fits - that is the entire process; no data changes and no software is required. Some astronomy stacking and plate-solving programs require the .fits extension even though the format is identical to .fit.

1 programs
Also to FITS: SPE · FTS

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Tested on macOS, Windows & Linux
Last verified Oct 2026

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Why convert FIT to FITS?

FITS (Flexible Image Transport System), the standard scientific image format since 1981, is identified by three equivalent extensions: .fit, .fits, and .fts. The IAU standard does not mandate a specific extension, but .fits is the most widely expected by astronomy stacking software and plate-solving pipelines. Software that rejects .fit files does so only because of extension filtering, not any difference in the binary format.

How to convert FIT to FITS

ImageJ OPEN-SOURCE

If renaming alone does not resolve compatibility, open the .fit in ImageJ and use File > Save As to write it with a .fits extension.

Programs that convert FIT

ImageJ

About these formats

.FIT Flexible Image Transport System (FITS) image

A .fit file is a FITS (Flexible Image Transport System) astronomy image - the standard scientific data format used by telescopes, astrophotography cameras, and research archives since 1981.…

Open .FIT details →
.FITS Flexible Image Transport System File

A FITS file is the standard scientific image format used by telescopes, astrophotography cameras, and archives such as NASA and ESA. Open it with SAOImageDS9 (free) or NASA FITS Liberator.…

Open .FITS details →

Quality & what to watch

  • .fit, .fits, and .fts are identical at the binary level - renaming does not alter any pixel data or header content.
  • Do not confuse astronomy .fit files with Garmin FIT activity files (GPS and workout data); they share the extension but are completely unrelated formats.
  • The FITS ASCII header is readable in a plain text editor, making it easy to confirm the file is a real FITS image before renaming.

Frequently asked questions

Why does my astronomy software refuse `.fit` but accept `.fits`?
The software filters by extension rather than format content - renaming the file to .fits resolves the issue because the binary format is identical.
Will renaming corrupt or change the image data?
No - renaming changes only the extension string; every bit of the FITS header and pixel data remains untouched.
Is `.fts` also the same format?
Yes - .fts is a third alias for FITS, equivalent to .fit and .fits in every way.