I am trying to partition a new external drive with 4 TB capacity with MacOS 12.5.1 & Disk Utility to a Windows-compatible format (MSDOS etc.). But no matter how to "erase" the disk, I am not able to partition the disk. It always says "This volume can’t be resized." and I neither can add or remove a partition.

enter image description here

How can I partition this external drive into 2 partitions of equal size in a windows-compatible format?

  • I too find this really odd. This app seems to let us erase a disk, but not control how many partitions the newly erased disc will have, and then not change the number of partitions -- but seems to have the tools in theory to change partitions.
    – Magnus
    Commented Jan 22 at 2:26

2 Answers 2


Maybe this GUI is not the best tool to work with disks, so here is how I managed to partition the external disk using the command line tool diskutil.

First, you need to get a list of all devices using the command

diskutil list

Then you erase your disk using the ExFAT format, like

diskutil eraseDisk ExFAT BACKUP /dev/disk3

(where you replace /dev/disk3 with your proper location), and finally you partition the disk using the command

diskutil partitionDisk /dev/disk3 2 MBR  ExFAT BACKUP1 2000G ExFAT BACKUP2 0

In the latter I use 2 partitions with the first having 2 TB of space and the second partition the rest (hence the "0").

That process seem to have worked for me ...


OK, after playing around with Disk Utility, I figured out how to partition a disk with different kinds of file system. It's not intuitive.

The key thing to understand is that Disk Utility will ONLY resize partitions of type APFS. Once you create a partition of type e.g. EXFAT, you can't resize it with Disk Utility.

Let's say that you have a USB flash drive and you want 4 partitions of type EXFAT, MSDOS, etc. You first erase the disk and choose APFS. This will create a single partition of that type. Now you can select the disk, go to the partition menu, and start adding partitions. As long as you leave the type 'APFS', you can resize them. So leave the partitions under type APFS while you adjust the sizes. Only when you are happy with the sizes do you change the type of each partition to your final desired type (EXFAT, etc.).

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .