Extend C drive

How to extend C drive in Windows 10

Windows Updates, services, applications and many other kinds of files write into system C: drive continuously every day. Sooner or later your C drive becomes full, especially when C drive was created less than 40GB. Several days ago, a reader of my blog ask for help, because the C drive was created as 80GB but now is running out of space.

The fast way to solve this problem is by resizing partitions. Shrink other disk volumes to get free space and then add into C drive. Some Windows 10 users feedback they don’t know how to resize disk partition and worry about data safety. In this article, I’ll introduce how to extend C drive in Windows 10 without data loss.

Extend C drive

Tips before extending C drive

There are several points you should know before extending C drive in Windows 10, otherwise, it may cause trouble:

  1. Check if there is free space in any other volume in the same disk.
    No partitioning tool can resize partitions beyond 2 hard disks. That is to say, the volume that take free space to expand C should be in the same hard disk.
  2. You’d better close other running applications before extending C drive.
  3. Pay attention to data safety.
    Different with read-only operation, to resize and extend volume, the partitioning tool will modify all parameters related to this disk, partition and all files in the volume. A slight error may cause data loss, so it is important to select a reliable tool.

How to extend C drive in Windows 10

To extend system C: drive in Windows 10, there are two choice: Windows built-in Disk Management and 3rd-party application. Because of the limitations of Disk Management, I always recommend 3rd-party application such as NIUBI Partition Editor.

Expand C drive in Disk Management

The precondition to expand C drive: there must be adjacent Unallocated space on the right side. Some people try to shrink the adjacent volume D with Shrink Volume and got some Unallocated space, but when right clicking C drive, Extend Volume is grayed out.

To extend volume with Windows 10 Disk Management, the only option is deleting volume to get Unallocated space. (Actually, it is not suggested)

Steps to extend C drive with Windows 10 Disk Management:

  1. Back up or transfer all files in volume D or other one that is right next to C drive.
  2. Right click Window icon on bottom left corner and select Disk Management.
  3. Right click volume D and select Delete Volume to get Unallocated space.
  4. Right click C drive and select Extend Volume.
  5. Finish the Extend Volume Wizard and then C drive will be extended.


  1. The applications and Windows services that points to volume D stop working.
  2. In some situation, you cannot get adjacent Unallocated space even if deleting D, of course you cannot extend C drive in that case. See why Extend Volume is disabled.

Extend C drive with professional partition software

With NIUBI Partition Editor, it is much easier and without limitations. To resize and extend volume in Windows 10, you just need to click and drag on disk map of this program. Beside resizing disk drives, it also helps do many other operations, such as copy, convert, defrag, wipe, active, label, check partition, etc.

How to extend C drive on Windows 10 with NIUBI:

Download NIUBI Partition Editor and you’ll see all local and removable storage device that are connected to this computer.

Step 1: Right click drive D (or other adjacent drive) and select Resize/Move Volume:

Shrink D

In the pop-up window you’ll see size and location of D on the top and disk partition layout on the bottom.

Original drive D

Drag the left border rightwards to release free space from D.

Shrink D

Click OK and back to the main window, 20GB Unallocated space is generated behind C drive. (If you drag right border of D leftwards, Unallocated space will be generated behind D)

Unallocated created

Step 2: Right click C drive and select Resize/Move Volume again. In the pop-up window, you’ll see C drive and the adjacent 20GB Unallocated space:

C drive and Unallocated

Drag the right border rightwards

Extend C drive

20GB Unallocated space is combined into C drive.

Merge Unallocated

Step 3: Click OK and back to the main window, press Apply on top left to proceed, done. C drive is extended to 59.4GB by getting 20GB free space from D.

C drive extended

Tips: If there is not enough free space in volume D, you can get from any other volumes in the same disk, just need an additional step to move partition.

Watch the video how to resize partition and extend C drive in Windows 10:


Download to try