How to recover lost disk space on a USB drive

  • By Christopher Kielty, last updated September 07, 2016
  • Filed under: Windows Mac

If you’ve ever copied a disk image to a USB thumb drive, you may have have run into the mysterious problem of disappearing disk space. This is normal after you’ve copied an image to the drive. However, if you one day want to reclaim that drive for some other use, it may look as though that extra space is just gone. Don’t worry. It’s not.

When the partition scheme is changed, the size of the drive may appear to have changed. If this is the case, even formatting the drive won’t get the missing space back. I have heard of this happening on Windows more than anything else. I have included instructions here for both Windows and Mac OS X.

In order to correct this problem, we need to repartition the drive, then reformat it. That’ll restore the drive to it’s original glory.

Before proceeding, please be sure to back up all of your files. While I don’t expect anything to go wrong, it’s always better safe than sorry.

Windows

If you’re on a Windows machine, keep reading. Otherwise, skip to the next section for Mac OS X.

Open the utility called DiskPart. It should be included with your Windows system. You can get to it by going to Start, then typing in diskpart.

DiskPart should open now in a command line window.

Type list disk into the command prompt and hit enter.

You should see several disks labeled Disk 0, Disk 1, etc., and their corresponding size. We want to choose the disk that’s the same size as your USB drive. Once you know which one, type select disk # (replace the # with the actual disk number). Please do take care that you’ve selected the correct disk. Selecting an incorrect disk could result in lost data.

Now type clean to reset the partition.

Once that command completes, you should see a message saying something to the effect of DiskPart succeeded in cleaning the disk.

Now type create partition primary.

It should take just a few moments to create the partition. Once that’s done, you’ll see a message saying something like DiskPart succeeded in creating the specified partition.

All done. Now type exit, hit enter, and DiskPart will close. Your disk should be back to normal now!

Mac OS X

OS X Disk Utility

On OS X we're going to use Disk Utility. You can find this handy app in the /Applications/Utilities/ directory. It is also easily accessed by opening Spotlight (press command + spacebar) and typing Disk Utility. Actually, just typing in disk u will probably bring it up. One of the many perks of Spotlight.

Next, click on the disk you want to repartition. Click the Partition tab, then select "1 Partition". Make sure the size of the partition is about the same size as the actual disk.

Set the partition size in Disk Utility

Now just hit Apply and you're done!