USB erased, unable to partition because 18.4 MB used space

Unlike other operating systems you don't partition and format a drive using Disk Utility anymore using the "Partition" tab of Disk Utility (Apple Thinks Different). You need to select the physical drive on the left pane of Disk Utility and "erase" it as GUID partition and FAT32/MSDOS, exFAT, or MacOS Extended (Journaled) depending on the file system you prefer to use. You may need to click "View" within Disk Utility and select "Show All Devices" so that the physical drives appear on the left pane of Disk Utility.

I finally had time to try it out and it doesn't appear you can partition an MS-DOS (FAT32) drive. The used space has nothing to do with it.

While rather odd, I was able to make the first partition Mac OS Extended (Journaled), then create FAT32 partitions after it. After setting all the sizes, I could change the Mac OS Extended to FAT32. Start with erasing the entire drive as Mac OS Extended, then Partition it as desired. Make sure you set the size of the first partition before changing to FAT32 as you won't be able to change it after selecting FAT32 for the format.

Interesting......

For me, Once you have a single partition, then the partition tab does work to allow you to add more partitions or to delete partitions back to a single partition. Of course USB sticks and many external drives ship with at least one partition by default. To experiment, If you want a blank drive with no partitions you can use "dd" to write zeroes to the beginning the physical drive in order to destroy the current partition table, then see if the partition tab is available. I believe it was macOS 10.11 when Apple changed how the "Partition" tab worked with truly blank drives.

I've faced this a number of times. My fix is to move the files to a temporary location on a different disk, delete them on the disk, erase the partition in question and then repartition the drive as needed.

Once partitioned, move the files back to the appropriate partition.

Barney-15E wrote:

Unlike other operating systems you don't partition and format a drive using Disk Utility anymore using the "Partition" tab of Disk Utility

That makes absolutely no sense at all. You cannot use "Erase" to partition a drive.

I know, but this is how Disk Utility works with macOS 10.11+. If you have a completely blank drive, then the only way you can "partition & format" it with Disk Utility from macOS 10.11+ is by using the "Erase" tab in Disk Utility. The "Partition" tab in Disk Utility for macOS 10.11+ will be grayed out and inaccessible (I just verified this again today while booted to a Big Sur installer). The "Partition" tab only becomes available if there is at least one partition already on the drive.

Disk Utility in macOS 10.10 and earlier behaves like Windows and Linux where a blank drive must first be partitioned, then formatted with a file system.

For me, Once you have a single partition, then the partition tab does work to allow you to add more partitions or to delete partitions back to a single partition. Of course USB sticks and many external drives ship with at least one partition by default. To experiment, If you want a blank drive with no partitions you can use "dd" to write zeroes to the beginning the physical drive in order to destroy the current partition table, then see if the partition tab is available. I believe it was macOS 10.11 when Apple changed how the "Partition" tab worked with truly blank drives.

I haven't had a bare drive in more time than I can remember.

Thanks for your help. I believe this whole disk has to be fat32, as I’m trying to use this as a storage usb for my Firestick.

All partitions were FAT32 in the end. I don’t understand why you need to partition it, though. My guess is you’ll need the MBR partition map for the Firestick.

Is there data on it that you are trying to retain?

Oddly, I managed to do what you said I couldn’t when I created the example I mentioned above.

I have no idea why Disk Utility keeps adding stuff into my disk

Disk Utility doesn't do that. Spotlight and the File System create those.

Maybe try using MBR partition map instead of GUID. Disk Utility is fairly limited with FAT32.

Unlike other operating systems you don't partition and format a drive using Disk Utility anymore using the "Partition" tab of Disk Utility

That makes absolutely no sense at all. You cannot use "Erase" to partition a drive.