Extend hard drive

3 options to extend Windows 10 C drive partition

It is very common that the system C: drive runs out of disk space, no matter you use Windows 10 desktop or laptop, use SSD or traditional mechanical hard disk drives. If there is free unused space in other partition in the same disk, you can extend C drive without losing data or reinstalling OS. This article shows 3 options to extend C: drive on Windows 10 with native and 3rd-party partitioning tool.

Extend C drive

Option 1 Extend C drive by deleting D

Windows 10 Disk Management has built-in Extend Volume functionality which can be used to extend C drive or any data partitions. However, there is precondition: Extend Volume is workable only when there is adjacent Unallocated space on the right side of the partition that you want to expand.

In Windows 10 native Disk Management, there are 2 options to get Unallocated space by deleting or shrinking. All disk space of a partition will be converted to Unallocated after deleting, but only part of unused space will be converted to Unallocated by shrinking. That means, partition size decreased and files keep intact.

Obviously, it is better to extend disk partition by shrinking other drives, but you can’t extend C drive in Windows 10 Disk Management by shrinking D. When you decrease drive D with another built-in Shrink Volume functionality, Unallocated space can only be produced on the right side of D, but to extend C drive with Extend Volume, the Unallocated space must be on the left side of D.

Extend Volume greyed out

Thus, if you want to extend C drive with Windows 10 Disk Management, the only option is by deleting the adjacent drive D.

Caution If you install programs to drive D, do NOT use this method.

If you did not install any program in drive D, follow the steps to extend C drive:

  1. Back up or transfer all files in partition D.
  2. Right click Windows on bottom left corner and select Disk Management.
  3. Right click drive D and select Delete Volume.
  4. Right click partition C and select Extend Volume, finish the Extend Volume Wizard by simply clicking Next.

Option 2 Extend C drive by merging D

With professional disk partition software such as NIUBI Partition Editor, there is easier method by merging the adjacent partition D. Everything in D will be moved into C drive automatically.

Download NIUBI Partition Editor, right click drive D and select Merge Volume.

Merge Volume

In the pop-up window, click the check-box in front of both drive C and D.

Select drives

Click OK and back to the main window, as you see, C drive is extended to 111.3GB. Press Apply on top left to execute.

C drive extended

All files in original drive D will be moved to a folder in C named as “D to C” automatically.

Tip It is NOT suggested to expand C drive on Windows 10 by merging other drive, you’d better keep a separate partition in the same disk.

 Extend C drive by shrinking other drives

The best option to increase C drive space is by shrinking other partition (no matter it is adjacent or not).

Step 1 Right click D drive and select “Resize/Move Volume”.

Resize volume

Drag the left border rightwards to shrink it.

Shrink D

Unallocated space is generated on the left side.

Unallocated space

Step 2 Right click C drive and select “Resize/Move Volume” again, drag the right border rightwards to hold the Unallocated space.

Drag to extend

C drive is extended to 94.65GB, click Apply to execute, done.

C drive extended

Watch the video how to extend C drive on Windows 10:

In Summary

If you want to extend C drive with Windows 10 built-in Disk Management utility, the only option is deleting the adjacent drive (D). This destructive way is not suggested, you’d better shrink D instead. You won’t lose partition and everything keeps the same. If there is not plenty of free space in drive D, you can get free space from any other partitions in the same disk. If there is no other partition in this disk, you can clone it to another larger one with NIUBI Partition Editor, and then extend C drive with extra disk space.


3 options to extend C drive partition on Windows 10 with detailed steps.
4.8 (95%) 4 votes