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I've been looking around for a way to do this for a while, but I haven't been able to find the answer. I need to format my 2 GB SD card to FAT-32, but I don't see the option in Disk Utility.

If I select the SD drive (Apple SDXC Reader Media) and go to 'Erase,' I have the following format options:

  • Mac OS extended (Journaled)
  • Mac OS extended (Journaled, Encrypted)
  • Mac OS extended (Case sensitive, Journaled)
  • Mac OS extended (Case sensitive, Journaled, Encrypted)
  • MS DOS (FAT)
  • ExFAT

Doing the same, but selecting the SD card itself (in my case, NO NAME), I get all the same results, minus Mac OS X's with encryption.

I have read that selecting MS-DOS will chose between FAT-16 and -32, depending on the SD card's size. However, I have a 2 GB one.

Format:            MS-DOS (FAT16)
Owners Enabled:    No
Number of Folders: 0
Capacity:          1.98 GB (1,975,546,368 Bytes)
Available:         1.79 GB (1,789,296,640 Bytes)
Used:              186 MB (185,991,168 Bytes)  --> (I have already backed up)
Number of Files:   512
Peter Mortensen
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Matt Reynolds
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  • Seems like disk numbers greater than 1 should be used in all answers to this lest users erase their main drive. I know most main drives are disk0s but still, let's add a margin of safety – JohnAllen Feb 29 '16 at 17:08

4 Answers4

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If you're comfortable with using the Terminal, try this:

First, look at the partition table by running this command:

diskutil list

You should see something like this:

/dev/disk1
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *16.0 GB    disk1
1:                        EFI                         209.7 MB   disk1s1
2:                  Apple_HFS Example                 15.7 GB    disk1s2

The partition we want to change is /dev/disk1.

We want to change the device to an MBR-formatted FAT32 partition. To do that, run this command:

sudo diskutil eraseDisk FAT32 NAME MBRFormat /dev/disk1

where NAME is the name you want to give to the disk.

As mentioned in the comments, you cannot put square brackets into the volume's name lest things mess up. To avoid having everything fail, simply ensure that there are no square brackets in the FAT32 volume's new name.

Note: The NAME can fail if not UPPERCASE in many cases.

Joshua Michael Calafell
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Alex Plumb
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  • When I did the 'diskutil list' command, I got the following for disk1: `/dev/disk1 #: TYPE NAME SIZE IDENTIFIER 0: FDisk_partition_scheme *2.0 GB disk1 1: DOS_FAT_16 NO NAME 2.0 GB disk1s1` With the second command, I got: (In next comment) – Matt Reynolds Jan 03 '13 at 18:38
  • `Started erase on disk1 Unmounting disk Creating the partition map Waiting for the disks to reappear Formatting disk1s1 as MS-DOS (FAT32) with name [NAME] newfs_msdos: [NAME]: bad volume name Mounting disk Could not mount disk1s1 with name (null) after erase Error: -69832: File system formatter failed` (Yeah, I left it as [Name] cuz I was in a hurry) – Matt Reynolds Jan 03 '13 at 18:41
  • And it doesn't show up in finder, and plugging it in brings up a window saying "The disk you inserted was not readable by this computer" and the buttons "Initialize," "Ignore," and "Eject." – Matt Reynolds Jan 03 '13 at 18:44
  • Nevermind, I figured it out. I tried to repair, which failed, so I made a new partition, deleting the old one. After that, I re-tried your idea, and it worked! – Matt Reynolds Jan 03 '13 at 19:48
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    I've learned something today: if you try to put square brackets into a FAT32 volume name, things will break badly. – Alex Plumb Jan 03 '13 at 20:08
  • Ah. I guess that's where things went wrong. Thanks! – Matt Reynolds Jan 04 '13 at 15:43
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    If the SD card is write-protected the result is a rather misleading error message. Perhaps you can include that in the answer? – Peter Mortensen Dec 25 '15 at 18:14
  • you might suggest usage of `diskutil info ` as a way to verify the correct disk, the output from diskutil list can be pretty obscure – random-forest-cat Dec 20 '18 at 01:26
  • Please don't use `/dev/disk1` as your example, as this is the Macbook hard drive. No I didn't just format it, but someone might. – geotheory Jul 03 '19 at 10:07
  • Also volume name needs to be ALL CAPS. Sometimes it's just been a long day... – hashlock Sep 15 '19 at 00:33
  • Thanks, its so aggravating to try and update firmware on Samsung monitors and it still can't find the *.img file. – Mark Nov 23 '21 at 17:04
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sudo diskutil eraseDisk FAT32 [NAME] MBRFormat /dev/disk1

Where [NAME] must be written in CAPITAL letters; otherwise, this will not work.

As mentioned in the comments, ensure that you use a tool such as diskutil to check which disk you are formatting. In the example above, the disk /dev/disk1 is being formatted. After finding the desired partition through a method such as calling diskutil list (This command lists the partitions on the system. See other answer for details), replace dev/disk1 with the desired partition.

Matt Reynolds
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pecuequin
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    This answer is pretty risky if you haven't first used some tool like diskutil to determine which device your SD card is. On my machine, the SD card is /dev/disk2. Good thing I didn't follow this answer blindly! – LarsH Jan 19 '15 at 16:48
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    If the SD card is write-protected the result is a rather misleading error message. Perhaps you can include that in the answer? – Peter Mortensen Dec 25 '15 at 18:15
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If you tried this:
$diskutil eraseDisk FAT32 MYDISKLABEL MBRFormat /dev/disk1

But receive this error:
FAT32 does not appear to be a valid file system format Use diskutil listFilesystems to view a list of supported file systems

Then this answer may help you.  But please note:

  • This is an alternate solution for older Apple Mac versions where FAT32 as the filesystem type does NOT WORK as per the error above.  
  • I am not sure which "older" versions produce the error, but it does occur in Snow Leopard 10.6.8 with diskutil version dated 15 May 2009.
  • The error may occur from Mac OS Leopard 10.5 to Yosemite 10.10.  
  • This solution is not relevant for newer Mac OS versions, perhaps El Capitan 10.11 and onwards.
  • In the following examples, /dev/disk1 points to the SD card (device).  You need to determine what is the pointer to your device.
  • I will not elaborate on every bit of information, just what changes need to be made to your command; e.g. you should know from other answers when to use sudo, how to identify your device, how to unmount your device, how to specify the label and how to verify that the disk is formatted correctly.
Command Line Syntax:
diskutil eraseDisk filesystem disklabel MBRFormat device


Solution:
Find the correct filesystem alias by listing all available options:

$diskutil listFilesystems

In the output table you will see that there are aliases defined by "(or) something" but there is no alias for the "FAT32" filesystem.  Thus, you must specify the case-insensitive full name "ms-dos fat32".

Command:
$diskutil eraseDisk "ms-dos fat32" mydisklabel MBRFormat /dev/disk1

rwarvi
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    this save me for long day of reaserach you deserve the upvote – Espoir Murhabazi Nov 19 '17 at 09:12
  • Hm, FAT32 worked for me. MacOS Catalina 10.15.2. – kelin Jan 14 '20 at 12:59
  • This did get around message "Unknown partition scheme: MYDISKNAME ". After I get `mydiskname does not appear to be a valid volume name for its file system` (high sierra). gderaco's answer worked though, or using the name in all capitals like MYDISKNAME – rogerdpack Apr 29 '21 at 00:31
  • `diskutil eraseDisk "ms-dos fat32" mydiskname MBRFormat /dev/disk1` fails but `diskutil eraseDisk "ms-dos fat32" MYDISKNAME MBRFormat /dev/disk1` succeeds :) – rogerdpack Jun 04 '21 at 15:35
  • @rogerdpack, so that I can improve my answer, please send me your OS X version and diskutil version number/date from the man page. – rwarvi Jun 18 '21 at 06:00
  • @kelin, your feedback is appreciated. Please send me the diskutil version information on your Catalina 10.15.2. – rwarvi Jun 18 '21 at 06:04
  • @rwarvi, sorry bro, I updated my macOS since the time of that comment. – kelin Jun 19 '21 at 18:07
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For me, none of the posted answers worked. What worked instead was

diskutil eraseDisk JHFS+ UntitledUFS /dev/disk2

and then from the Disk Utility UI format it again to FAT32.

rwarvi
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gderaco
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