I plugged in a 250GB USB hard drive into my MacBook Pro and want to format it in FAT so I can transfer files back and forth between a windows machine.

(My windows7 machine only formats in exFAT which my Snow Leopard 2.6.4 doesn't support until I do the update).

So I want to format it on the mac.

but when I right click on the drive, it gives me the options to eject, copy, but not to format.

I can go into Disk Utilities, click on Partition, but the only option is the "Mac Journaled format".

How can I Format my USB drive as FAT from my MacBook Pro?


In Disk Utility select the drive that you want to partition, then the Partitions tab.

To make FAT and ExFAT available in FORMAT you need to change Volume Scheme from Current to 1 Partition.

You might also want to check under Options... that the partition scheme is Master Boot Record. I've happily formatted a USB to FAT32 using the Apple Partition Map (a hangover from creating an Ubuntu Live USB). My Mac would happily read the resulting FAT32 volumes but Windows of any flavour refused to read it.


You can't without splitting the drive into smaller partitions.
FAT has a max volume size of 32GB, meaning a 120GB drive cannot be formatted as FAT as a whole.
If you have the money or if you don't really have many large files, I would use a cloud service like Dropbox or one of its competitors.

  • 1
    I think you both mean fat32. The file system has a technically maximum size of 8TB (on a cluster size of 32KB): 2^15byte (=32KB) * 2^28 (max. cluster count causing from 32bit adressing (4bits are reserved)) = 2^43byte), but on windows its limited 32GB, beacause higher sizes would cause a big performance loss. – schöppi Nov 11 '10 at 22:51
  • I generally refer to FAT32 as FAT just like people refer to email as mail. – digitxp Nov 13 '10 at 22:08

As digixp said, formatting such "big" drives with FAT32 doesn't working/doing well. Dropbox is a nice idea, but because of it's limited space you can also use some usb stick with 32gb space. ;)

So I would suggest to use a NAS with smb access. Don't know how good it's working on MacOS, but if you want to play it safe you're doing well with Apples Time Capsule.


I know little of MacOS (though I'm sure it is likely to be able to format large FAT32 partitions). If it doesn't you could boot your Windows machine using an Ubuntu (or any other Linux distro) Live CD and format it from there. Linux will happily format a FAT32 partition up a few terebytes.

Or you could try find a Windows 98 installation as this didn't have the artificial 32Gb limit (though IIRC there was a limit due to certain bugs, 512Gb rings bell).

Once properly formatted Windows will happily use a FAT32 filesystem created by another OS.

Remember though to be wary of the limitations of FAT32 especially on large partitions: it is very inefficient in terms of space use for small files and badly prone to fragmentation (though depending what you use the drive for this may not be a problem for you), there is no journalling at all (unlike NTFS, ext3/4 and other modern filesystems) so be extra sure that you properly sync/umount/eject the drive before unplugging lest the filesystem become corrupt, and so on.

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