Reason 1

Cannot extend volume into Unallocated space

This article explains why Windows Disk Management can’t extend volume into Unallocated space, as well as the easy solutions to fix this issue. The reasons and corresponding solutions are valid for Windows 10/8/7/Vista/XP and Server 2019/2016/2012/2008/2003 (R2).

From Windows XP and Server 2003, you can extend disk partition via DiskPart command prompt without losing data. However, command line seems to be difficult to some users, in addition, Unallocated space won’t be shown in command prompt. To enhance the ability and make it easier to use, Microsoft provided the GUI Extend Volume feature to accomplish this task from Windows Vista.

It is a good start, but there is no other improvement over 10 years. Because of the inherent limitations, you still cannot extend most of partitions with Extend Volume. The typical example is that you can’t extend volume to Unallocated space that shrank from other drives. In this article, I’ll show you the common reasons and the corresponding solutions one by one.

Reason 1 No adjacent Unallocated space

A 256GB hard disk can’t be increased to 512GB, so before extending a hard drive partition, you must get Unallocated space by deleting or shrinking another drive. If you right click a drive without Unallocated space in the same disk, Extend Volume is greyed out. Furthermore, Unallocated space must be adjacent to the drive that you want to extend, otherwise, Extend Volume doesn’t work.

Together with Extend Volume, there is Shrink Volume functionality to decrease a drive and convert part of free space in this drive to Unallocated. However, Shrink Volume can only shrink a drive towards left and produce Unallocated space on the right side.

Cannot extend volume

As you see, the 20GB Unallocated is nonadjacent to drive C after shrinking D, so I cannot extend volume C into Unallocated space.

Solution 1 Move Unallocated space to the other side.

In this situation, you need 3rd party disk partition tool to move this 20GB Unallocated space to the other side, then Extend Volume will be enabled for C drive.

Download NIUBI Partition Editor, you’ll see all disk partitions on the right and available operations to highlighted disk or partition on the left side.


Steps to fix can’t extend volume to Unallocated space:

Step 1: Right click drive D and select “Resize/Move Volume”, drag the middle position towards the other side in the pop-up window.

Move D

Click OK, 20GB Unallocated space is moved to the left side of D.

Unallocated moved

Step 2: Right click C drive and select “Resize/Move Volume” again, drag the right border rightwards in the pop-up window.

Extend C

Click OK, Unallocated space is combined to C drive.

System drive extended

Tip NIUBI Partition Editor is designed to work in its virtual mode, to modify real disk partition, you need to click Apply to take effect. If you changed your mind, simply click Undo to cancel the pending operations.

Reason 2 Unallocated space must be on the right side

In fact, besides adjacent, Unallocated space must be on the right side. Disk Management cannot extend partition into Unallocated space that is on its left. As you see, Extend Volume is disabled for drive E.

Unallocated on left

Solution 2 In this situation, you just need 1 step to merge the Unallocated space to drive E.

Right click drive E and select “Resize/Move Volume”, drag the left border leftwards in the pop-up window:

Extend E

 Not supported partition

In fact, both Extend Volume and Shrink Volume functionalities support NTFS only, they can’t extend FAT32 partition into Unallocated space even if the Unallocated is right adjacent.

FAT32 not supported

Solution 3 In this situation, simply combine the 20GB Unallocated space into drive D with NIUBI Partition Editor.

Right click drive D and select “Resize/Move Volume”, drag the right border rightwards in the pop-up window.

Extend drive D

In Summary

Because of the inherent limitations of Shrink and Extend Volume, Disk Management (and DiskPart Command) can extend a partition only when:

  • This partition is NTFS.
  • There is adjacent Unallocated space on the right side of the drive that you want to extend.

Otherwise, it cannot extend volume with Unallocated space. Luckily, with NIUBI Partition Editor, these issue can be fixed easily.