After I did steps shown here I've noticed in VM's settings that I only increased virtual size but actual size remain the same. How to increase it also?

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3 Answers 3


When you increase the virtual disk size, you typically have to increase some partition size within the OS's actual file system in order to make use of the added space. However, because you've set it to "dynamically allocated", it will grow as used. See http://www.virtualbox.org/manual/ch05.html which says:

"For more flexible storage management, use a dynamically allocated image. This will initially be very small and not occupy any space for unused virtual disk sectors, but will grow every time a disk sector is written to for the first time, until the drive reaches the maximum capacity chosen when the drive was created. While this format takes less space initially, the fact that VirtualBox needs to expand the image file consumes additional computing resources, so until the disk file size has stabilized, write operations may be slower than with fixed size disks. However, after a time the rate of growth will slow and the average penalty for write operations will be negligible."


This is still a valid question to this day, I was a bit confused. I expanded mine from 10GB to 20GB. But after opening the VM, nothing changed. This is because it was expanded as UNNALOCATED SPACE.

All I had to do, after expanding in VirtualBox settings, was:

  1. Open Disk Management on windows guest
  2. (now there will be unallocated 10GB because I expanded)
  3. right click the 10GB in-use partition
  4. click expand
  5. confirm dialogs etc. that's it
  • All the other answers and internet posts are confusing. This is right on the nail correct and clear answer on how to resize the damn disk. Basically you gotta resize from outside ( the vm disk allocation ) and than ( inside the guest OS ) resize their partition. It took me way to long to figure this out. Thank you very very very much mate. Dec 9, 2021 at 15:42
  • yes and virtualbox settings are hidden and confusing
    – obama
    Dec 14, 2021 at 4:15

Put it simple, if you copy a big file, say, 1 GB size to the virtual disk, the actual size will approximately increase 1 GB. To consume the diskspace will increase the actual size.

  • This appears to be a comment not an answer
    – Ramhound
    Nov 19, 2015 at 20:28
  • Maybe the answer is short, but I just want to point out the meaning of "actual size". No matter how you adjust your partition virtual size, with dynamic growing option on, the actual size only relates to your content size. Nov 24, 2015 at 6:47
  • As I said. The answers currently is a comment not an answer to the author's question. The author's question was specifically, "How to increase it also?", you don't explain how to increase it.
    – Ramhound
    Nov 24, 2015 at 12:14
  • @Ramhound, thank you, I edited, explicit on "how" Nov 24, 2015 at 19:57

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