Resize A VirtualBox Disk

To enlarge a virtual disk in VirtualBox, you’ll need to use the VBoxManage command from a Command Prompt window. First, shut down the virtual machine – ensure its state is set to Powered Off, not Saved.

Second, open a Command Prompt window from your Start menu and change to VirtualBox’s program files folder so you can run the command:

cd “C:\Program Files\Oracle\VirtualBox”

The following command will operate on the VirtualBox virtual disk located at “C:\Users\Goud\VirtualBox VMs\Windows 10\Windows 10.vdi”. It will resize the virtual disk to 81920 MB (80 GB).

VBoxManage modifyhd “C:\Users\Goud\VirtualBox VMs\Windows 10\Windows 10.vdi” --resize 81920

(Use two dashes before resize in the command above.)
Replace the file path in the command above with the location of the VirtualBox disk you want to resize and the number with the size you want to enlarge the image to (in MB).

Boot into your virtual machine, and you will realize that the drive still appears as being the same size as before (here, 15GB) !!! It’s normal — this is just because although the disk has been re-sized, the partition is still set up with its original size. We can fix it.

Go to the disk management by doing Start>Computer (right-click)>Manage>Storage>Disk Management.

Right-click on the existing partition you want to extend (here, C:) and choose “Extend Volume” in the pop-up menu.

By default, the Disk Manager will propose that you extend to all the available space, which is what you probably want to do, but you can pick any other size you want. 

And if all goes well, a new look at the C: drive now shows the 40GB we asked for. There you go. You can finally use the extra space!