How to merge Unallocated space to C drive in Windows 10

Published on: May 17, 2019

This article introduces how to merge unallocated space to C drive in Windows 10 (32 & 64 bit), how to move and add unallocated space to C drive without losing data.

C drive running out of space is very common to most of Windows computer users. The efficient way is allocating more free space to C drive from other partitions, then this problem can be solved fast without reinstalling Operating System and programs.

The same with previous versions, Windows 10 has built-in Shrink Volume and Extend Volume function in Disk Management console, which can resize disk partition on the fly. However, because of some inherent limitations, you can't shrink D to extend C drive. Many people tried to shrink D and made some Unallocated space, but Extend Volume is disabled for C drive.

In this article, I'll show you how to combine Unallocated space to C drive with Windows Disk Management and professional partition software. Add Unallocated space to C drive no matter it is contiguous or non adjacent.

How to merge Unallocated space in Windows 10 DM

In Windows 10 Disk Management console, you can get Unallocated space by deleting or shrinking a volume. By shrinking a partition, part of unused space will be converted to Unallocated, the files in this partition keep intact, so it is better than deleting.

But, Disk Management has serious limitations that cause you can't shrink D to expand C:

So, if you want to extend C drive with Disk Management, the only way is by deleting the contiguous partition (D:). To do this:

  1. Right click partition D and select Delete Volume.
  2. Right click C drive and select Extend Volume, simply click Next to finish the Extend Volume Wizard.

Two things you should know before doing this:

If you can't or do not want to delete partition D, you need third party software to move Unallocated space before adding to C drive.

How to move Unallocated space next to C drive

Download and install NIUBI Partition Editor, you'll see all connected disk with graphical partition layout and other parameters.

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

Windows 10 Disk Management cannot move Unallocated space or any partitions.

How to add Unallocated space to C drive

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

Extend C drive

As you see, Unallocated space is added into C drive.

Extend volume C

If you have not shrank D with Disk Management, you can make Unallocated space on its left side without moving Unallocated space to the other side. To do this:

Right click drive D and select "Resize/Move Volume", drag left border towards right in the pop-up window.

Shrink D

Then you can combine Unallocated space to C drive easily.

In Summary

If you have shrank partition D, Windows 10 Disk Management can't merge Unallocated space to C drive. Run NIUBI Partition Editor to move Unallocated space to the left side, and then add Unallocated space into C drive.

If you have shrank the non adjacent volume E with Disk Management, you need to move volume E and D one by one, and then merge Unallocated space to C drive.

If you have not shrank any partition, you can make Unallocated space on the left side of D with NIUBI and combine into C drive directly.

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