Extend C Drive with Unallocated Space in Windows 11

Running out of storage on your system drive can slow down your PC and prevent Windows updates from installing. This guide explains how to extend your C: drive partition in Windows 11 using adjacent unallocated space. Using built-in Windows tools like Disk Management and DiskPart, you can safely merge the unallocated space into your system partition without losing data or installing third-party software.

Method 1: Using Disk Management (Recommended)

Disk Management provides a graphical interface to quickly expand your system partition.

1. Open Disk Management: Right-click the Start button (or press Win + X) and select Disk Management.
2. Locate the C: Drive: Find your system disk (usually Disk 0). Ensure that the block of Unallocated space is directly to the right of the (C:) partition.
3. Extend the Volume: Right-click the (C:) partition and select Extend Volume.
4. Run the Wizard: Click Next on the Extend Volume Wizard welcome screen.
5. Select Space: The wizard automatically selects all adjacent unallocated space. If you want to use all of it, keep the default values. If you only want to use a portion, enter the amount in megabytes in the Select the amount of space in MB box.
6. Complete the Process: Click Next, then click Finish.

Your C: drive will immediately expand to include the newly allocated space.

Method 2: Using DiskPart (Command Line)

If you prefer using the command line or PowerShell, you can use the DiskPart utility.

1. Open Command Prompt as Administrator: Press Win + S, type cmd, right-click Command Prompt, and select Run as administrator.
2. Launch DiskPart: Type diskpart and press Enter.
3. List Disks: Type list disk and press Enter to see all connected drives. Note the disk number containing your C: drive (usually Disk 0).
4. Select the Disk: Type select disk 0 (replace 0 with your disk number) and press Enter.
5. List Partitions: Type list partition and press Enter. Note the partition number for the C: drive.
6. Select the Partition: Type select partition 1 (replace 1 with the correct partition number for C:) and press Enter.
7. Extend the Partition:
   • To use all available adjacent unallocated space, type: extend
   • To specify a specific size in megabytes, type: extend size=<size_in_MB> (e.g., extend size=10240 for 10 GB).
8. Exit: Type exit and press Enter to close DiskPart, then close the Command Prompt.

Important Requirements

• Contiguity: The unallocated space must be positioned immediately to the right of the C: drive on the same physical disk. If another partition (such as a Recovery Partition) sits between the C: drive and the unallocated space, the “Extend Volume” option will be grayed out in Disk Management.
• File System: The C: partition must be formatted with the NTFS file system, which is standard for Windows 11 system drives.