How to Recover Lost Space on a USB Drive

Joel Lee 09-03-2017

I play around a lot with my USB flash drives. They’re useful for so many things beyond just transferring files between devices. For example, you can use a USB drive to lock and unlock your computer as well as carry around portable apps everywhere you go Are USB Flash Drives Still Worth It In 2015? USB flash drives are great for storage, but they have so many other uses. Here's how they're worth their weight in gold. Read More .


As for me, I mostly use them as bootable drives for ISO files Create a Bootable USB From an ISO With These 10 Tools Want to create a bootable USB drive from an ISO file? We've got the ten best bootable USB pendrive creators around. Read More , which comes in handy when I want to try new flavors of Linux or turn a bricked laptop back into a Windows machine.

But I recently ran into a weird problem: I’m not sure how, but my 4 GB USB drive was suddenly showing up as a 100 MB USB drive. I’d lost a huge chunk of my drive’s storage capacity! Fortunately I found a fix, and if this has happened to you, rest assured that the fix is surprisingly simple.

As it turns out, the USB drive’s partitions had been tampered with, leaving most of the drive “unallocated” and inaccessible. That’s likely what happened to your drive. To fix this, we’ll just reset the partitions on the drive and “reallocate” all of the space as a new, single partition.

How to Recover Lost Space on a USB Drive diskpart reset partition usb drive

Before going ahead, back up your data! The following steps will completely wipe your drive. And make sure you pay attention to step 4 as you don’t want to accidentally wipe the wrong one!

  1. In the Start Menu, search for and launch diskpart.
  2. Type list disk to see all current disk volumes on your system.
  3. Plug in your USB drive and type list disk again. Note the newly listed volume.
  4. Type select disk # where # corresponds to your USB drive’s volume number.
  5. Type clean to wipe the volume of all partitions.
  6. Type create partition primary to make a new partition with all unallocated space.
  7. Type exit to finish.

If done correctly, your USB drive should be back to normal: a single partition with all of the space on the drive properly allocated and used. No more lost space!

Unable to reformat the drive? It might be write protected—here’s how to format a write-protected USB drive How to Format a Write Protected USB Pendrive Came across a write protected USB flash drive? Here's how to format your write protected pendrive and start using it again. Read More .

Related topics: Troubleshooting, USB Drive, Windows Tricks.

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  1. Janaka Priyadarshana
    June 13, 2020 at 10:23 am

    it's a very useful and successful step by step explanation, thank you , I've done

  2. The fixer
    January 16, 2020 at 2:56 am

    The part the author left out (or has changed since he wrote this).. After you have followed the steps above, do this:

    Make sure your usb hard drive is plugged in, Right click the start button, Go to disk management

    Find your device, right click on it, choose change letter and drive paths, name your device and select a letter for the drive

    Immediately windows should recognize the drive and ask you to format it so you can use it, select okay to format it, and done, your device is working!

    • Naveenkumar
      April 12, 2020 at 1:01 pm

      I get back the 16 GB pen drive, thanks for the instruction.

  3. azhar khan
    December 23, 2019 at 8:33 am

    I just did the step but i am not able to access of copy or paste any on my files in my pendrive i t is just showing write protected. kindly help

  4. Amadeu
    September 8, 2019 at 4:56 pm

    Very good tks !!

  5. Kiskocos
    June 4, 2019 at 4:07 pm

    i've done every step as instructed, but afterwards the Computer does not show the driver besides C and D (it would be the F).
    When i pluge it in it's deteced, I can hear the BEEP and it shows up among tools.
    The problem is that i can't reach it, open it.
    I would be greatfull if someone could help me whit this problem.

  6. Daniel Grey
    January 24, 2019 at 2:15 am

    Hi, I found this post very informative. Thanks a lot. However, something is not clear to me, Im sorry this might be a noob question, but what happens to the contents of the USB after fixing it? I mean, did you reformat the flash drive before fixing it? The thing is, I wanna know beforehand, so that I can prepare my recovery tool which is Acethinker Disk Recovery before doing your process. Thanks in advance for your response.

  7. Mohammed finan
    January 15, 2019 at 4:59 am

    Thanks,for your service

  8. John Smith
    November 11, 2018 at 8:34 am

    Thank you for posting this.

    It was easy to follow and worked perfectly.

  9. Kris
    September 9, 2018 at 1:40 pm

    This was a HUGE help. Thank you!

  10. Marcus
    August 28, 2018 at 3:43 pm

    Thanks a lot. Got back 100GB. Saved me a lot of money.

  11. Gaurav Srivastava
    August 8, 2018 at 3:59 pm

    It worked well, I have gained all the space 14.5 GB in 16 GB drive. Thanks.

  12. Anandh Jose
    July 19, 2018 at 5:09 pm

    Saved my day. Thanks a ton!

  13. Aadil
    January 11, 2018 at 5:13 pm

    it worked for really 4 gb usb drive showed unallocated space, i tried so many methods but nothing worked.i tried the above method & it worked.thanks a lot

  14. Anbarasan Devadass
    March 13, 2017 at 5:26 am

    Whenever I make Ubuntu 14 bootable USB my 16GB drive shrinked to 2MB. I use HPFormattingTool in windows to recover.

  15. William Vasquez
    March 10, 2017 at 5:03 pm

    You should also add this line at the end before 'exit'.
    format fs=Fat32
    This makes sure it is formatted to use right away.

  16. pajades
    March 9, 2017 at 7:37 pm

    COOL! I've had this "protected" 4GB USBdrive sitting on my desk at work for the past couple of years - numerous attempts to wipe it for reuse have failed... Until now! I now have an extra (usable) 4GB USB drive. Thanks!

  17. Tony
    March 9, 2017 at 6:16 pm

    You can also do a low level format on your usb stick to free up any space that's not accounted for.

  18. spyjoshx
    March 9, 2017 at 4:09 pm

    You can also do this with graphical tools like Gparted on linux, disk manager on windows, and disk tool on Mac.