How to extend c drive with diskpart cmd in Windows 10

Updated on: November 16, 2019

This article introduces how to extend C drive with DiskPart command in Windows 10. The introduction, precondition, steps to extend and limitations.

What is diskpart command

Diskpart is a command-line utility used to manipulate disk partitions in all versions of Windows clients and Windows Server beginning with Windows XP and Windows Server 2003. The utility adds capability to the Windows Disk Management snap-in. Users can type Diskpart commands directly to configure storage, or script Diskpart to perform multiple commands via a text file script, such as create, delete, format partition, convert basic disk to dynamic.

How to run Diskpart in Windows 10

There are two common ways to run diskpart command.

From cmd

  1. Press Windows and R on the keyboard.
  2. Type diskpart and press Enter.

Locate file

  1. Open C:\Windows\System32
  2. Double click diskpart.exe

Precondition to extend with Diskpart

Only when there is adjacent Unallocated space on the right side, you can extend C drive, otherwise, you'll receive error message 'There is not enough usable free space on specified disk(s) to extend the volume.'

Windows 10 diskpart has shrink command, but it cannot make Unallocated space on the left side when shrinking D, so extend command cannot extend C drive. The only option is by deleting the adjacent volume D.

However, it is not a good idea especially when Windows Services and applications are running from D. After delete, all shortcuts and part of programs will stop working even if you transfer all files in D to other partition.

How to extend C drive with diskpart cmd

Step 1: Type list volume in diskpart command prompt window and press Enter, you'll see all partitions but NO Unallocated space.

List volume

Step 2: Type select volume 1 to give focus to the system C: drive.

Select volume

Step 3: Type extend to proceed extending.

Extend volume

If you extend C drive again, you'll receive error message 'There is not enough usable free space on specified disk(s) to extend the volume.'

Cannot extend

Limitation of diskpart when extending C drive

  1. Only when there is adjacent Unallocated space on the right side, extend command is valid.
  2. Only NTFS partition is supported to extend.
  3. Unallocated space is not displayed in command window, so you don't know whether there is and where it is.
  4. Volumes are shown as list without structure.
  5. Operations cannot be undone, incorrect operation could cause data loss.

Because of the limitations, DiskPart command is not the best tools to resize partition and extend C drive on Windows 10. To do this, professional partition software is better choice.

Download NIUBI Partition Editor, you'll see all disks with partition structure on the right, available operations are listed on the left.

Main window

Step 1: Right click drive D and select "Resize/Move Volume", drag left border towards right in the pop-up window.

Shrink D

Then part of unused space is converted to Unallocated on the left side of D.

Shrink D rightwards

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 C drive is extended by merging the Unallocated space.

Extend volume C

This software is designed to work in its virtual mode, all operations you do will be listed as pending. So if you did something wrong, simply click Undo to cancel. To change real disk partitions, click Apply to execute.

Video guide to enlarge C: drive on Windows 10.

Besides resizing and extending disk partitions, NIUBI Partition Edition can help you do many other disk/partition management operations, such as merge, copy, convert, defrag, wipe, repair, scan, set Active partition, etc.