Can’t/unable to extend volume in Windows 10

Updated on: May 17, 2019

This article explains why cannot extend volume in Windows 10 Disk Management and what to do if unable to extend volume C drive after shrinking D.

Nowadays, many Windows 10 computers use SSD for Operating System and programs. It is helpful to improve computer performance. However, comparing with traditional mechanical disk, SSD is much smaller because it is still expensive. So the disk drives are more likely running out of space, especially to the system C drive.

The same with previous Windows 7, Windows 10 has its native Disk Management tool, which is able to shrink and extend allocated partition without losing data. So, many people try to shrink D to expand C drive.

In fact, Disk Management cannot extend volume C by shrinking D because of many limitations. In this article, I'll explain why you unable to extend volume in Windows 10 Disk Management, and how to solve this problem fast and easily.

Why cannot extend volume C

In one word: there is no adjacent Unallocated space behind C drive.

Before extending a drive, there must be Unallocated space. If you try to expand C drive without deleting or shrinking other drive to get Unallocated space, of course it is possible. (a 256GB hard disk can't be increased to 512GB)

To show you the limitations, I shrank D: drive in my computer.

Extend Volume greyed out

As you see:

  • I cannot extend partition C, because the Unallocated space is nonadjacent to it.
  • I cannot extend volume E, because Unallocated space is on the left side.
  • Only drive D meets the requirement, so Extend Volume is available.

Don't do this if you installed programs to D drive, otherwise, all shortcuts and part of programs will stop working even if you transfer all files in D to other partition.

Some people even tried to delete the adjacent partition D, but Disk Management still is unable to extend C drive. About this issue, it is more complicated.

To show you this limitation, I deleted volume D and then E on another computer. This time, disk space of drive D and E are shown as Free instead of Unallocated, system partition C still cannot be extended.

After deleting D

After deleting E

MBR GPT disk

This issue only exists on MBR style hard disk.

In MBR style disk, there could be maximum 4 Primary partitions, or 3 Primary partitions plus an Extended partition. These partitions work independently and have entry in the MBR sector. Logical partitions are simulated and just part of the Extended partition. So, after I deleting Logical partition D and E, the disk space is shows as Free.

Unallocated space deleted from Primary partition can't be combined to any Logical partition. Free space deleted from Logical partition can't be combined to any Primary partition.

What to do when can't extend partition C

In fact, it is very easy to solve this problem with professional disk partition software such as NIUBI Partition Editor. You just need to drag and drop on the disk map.

Solution: Move Unallocated space

As I explained above, Disk Management cannot extend partition C after shrinking D. In this situation, you need to move Unallocated space from right side of D to the left.

Download NIUBI Partition Editor, as you see, there is 20GB Unallocated space behind drive D.

NIUBI Partition Editor

Step 1: Right click drive D and select "Resize/Move Volume", drag middle position rightwards in the pop-up window.

Move drive D

Then Unallocated space is moved next to C drive.

Move Unallocated

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

Extend C drive

Then Unallocated space is combined into system C drive.

Extend volume C

Click Apply on top left to execute, done.

Watch the video how to move Unallocated space and extend C drive:

Video guide

Unable to extend volume E after shrinking D

As I show you above, Windows 10 Disk Management cannot extend volume E after shrinking D, because Unallocated space is on its left side. In this situation, you can combine Unallocated space into E drive with NIUBI directly, without moving partition.

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

Drag to extend

In Summary

Comparing with professional partitioning software, the native Disk Management is like a semi-finished utility. Because of the limitations of Shrink and Extend Volume, you cannot extend volume in most cases. With NIUBI Partition Editor

  1. When there is adjacent Unallocated or Free space on either side of C drive, simply drag the border towards other side to combine these space.
  2. When Unallocated space is non-adjacent to C drive, move Unallocated space to be contiguous and then combine.