I have medical records within Windows software within a DMG disk image. How can I convert the DMG to an ISO format on Mac OS X? Is it possible to do it within Disk Utility or CLI easily, or do I need an external utility?

4 Answers 4


You can use hdiutil to convert from .dmg to .iso directly:

$ hdiutil makehybrid -iso -joliet -o [filename].iso [filename].dmg

Renaming .cdr to .iso is bad advice! An .iso has a slightly different format that allows PC users to play the DVD as well. A renamed file will work on macOS, but NOT on a PC.

If you have a .cdr and want to convert it to an .iso, execute:

$ hdiutil makehybrid -iso -joliet -o [filename].iso [filename].cdr
  • 3
    Or you can just use the .dmg directly as input instead of going through .cdr.
    – dualed
    Commented Feb 12, 2015 at 17:37
  • yes, sure ;-) But please no renaming... Commented Feb 13, 2015 at 0:40
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    What would be the command to convert a dmg directly to iso just for completion sake of the question?
    – William
    Commented Mar 20, 2017 at 16:27
  • 1
    Does it work for creating a bootable Mac OS installtion iso image for VMWare?
    – Shayan
    Commented Sep 28, 2019 at 17:11
  • 3
    For anyone getting the error hdiutil: makehybrid: attach of disk image failed: 16, you need to unmount the image first (using Disk Utility).
    – Robert
    Commented Jan 9, 2020 at 9:24

Yes, Disk Utility can do this. Use Convert then select your dmg file. In the Save As dialog that follows, select DVD/CD master. Disk Utility will insist on saving the new ISO as a .cdr file, but it is really an ISO. You can rename it to .iso in the Finder, if you like.

At http://osxdaily.com/2012/07/18/convert-dmg-to-cdr-or-iso-with-disk-utility/ there are screen shots that walk through this process.

  • 4
    "it is really an ISO" is plain wrong. Seeing a .cdr from OSX, there appears to be no difference to a .iso . But you feel it after your DVD does not work on Windows. Commented Dec 8, 2014 at 13:57
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    I am still unhappy with the accepted answer. Both Sean and mblakele failed here, because an answer was accepted, that was only right for OSX users. But this will strike back, as soon as you try to use a renamed .iso in Windows. I think correctness is important, because wrong information should not be kept in the public, even if it's "just windows" ;-) Commented Aug 5, 2015 at 16:33
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    This is still wrong, today. What a shame! Commented Dec 2, 2016 at 18:41
  • @mblakele What convert button? Not seeing that on Disk Utility (version 16.0) . Am I doing this wrong, or is this answer just obsolete because of other software changes?
    – zipzit
    Commented Jan 29, 2017 at 17:19
  • @zipzit Apple likes to move things around from time to time. Try the Images menu, then Convert...
    – mblakele
    Commented Jan 31, 2017 at 4:58

Would be the same:

hdiutil makehybrid -iso -joliet -o [filename].iso [filename].dmg

For example:

hdiutil makehybrid -iso -joliet -o output_file.iso file_to_convert.dmg
  • Does it work for creating a bootable Mac OS installtion iso image for VMWare?
    – Shayan
    Commented Oct 1, 2019 at 20:22

You must mount the cdr people.

  • Welcome to Ask Different! Unfortunately, this doesn't look like an attempt to answer the question.
    – Glorfindel
    Commented Apr 12, 2017 at 16:23

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