USB flash drive shows incorrect size. Smaller

It appears that the USB is getting reported by the OS as having a GUID Partition Table (GPT). You can check this by looking at the drive properties Volumes tab and see what the reported Partition style is listed as. If it does list GUID then you’ll have to do some manual things to return the USB to a single MBR volume since the OS doesn’t let you remove volumes on a removable media directly.


  1. Open DOS command box in administrator mode. In Windows 8, search for CMD and then right click on it and select “Run as Admistrator”.
  2. At command prompt, type “diskpart”.
  3. Type list disk to see your disks.
  4. You can also open the Computer Management > Storage > Disk Management and verify the Disk number of the USB drive
  5. Then type “select disk 5” replace the 5 with your USB disk number
  6. Type “clean” and this will remove all volumes on the current in-focus disk by zeroing sectors. As such any files you have on their will also be lost.
  7. Go back to Disk Management, and the OS should now report the USB drive with the near total size but as “Unallocated”.
  8. Right click on the “Unallocated” for the USB drive and select New Simple Volume.
  9. Follow the wizard to partition the drive. Ensure you select File System FAT32.
  10. With a new healthy volume, right click and Format the USB drive. Since most of my USB sticks are now 4GB or greater I use NTFS as the format.

Then remove the USB drive and plug it into another Windows 7/8 machine and it should now report the proper volume and disk size.

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