When your Windows PC starts running out of space, extending the C drive is often the most effective way to restore system performance. However, many users encounter a frustrating issue: the Extend Volume option is greyed out even though unallocated space exists.
This Resize-C guide explains how to add unallocated space to C drive when Extend Volume is greyed out by identifying different disk layout cases and applying the correct solution for each scenario.
Windows Disk Management can only extend a partition if the unallocated space is located directly to the right of the target partition. If this requirement is not met, the Extend Volume option becomes unavailable.
Disk layout example: C Drive | D Drive / Recovery | Unallocated Space
This is the most common reason Extend Volume is greyed out. Windows Disk Management cannot move partitions, so it cannot place unallocated space next to the C drive.
IM-Magic Partition Resizer is one of the most effective tools for fixing the “Extend Volume greyed out” problem because it allows you to move partitions without deleting data.
Why IM-Magic Partition Resizer Works
Video: How to fix extend volume greyed out in Disk Management
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Steps to Add Unallocated Space to C Drive Using IM-Magic Partition Resizer
Note: Once the unallocated space is next to the C drive, the extension completes successfully—no greyed-out option.
✔ Best solution if you don’t want to delete partitions
✔ Safest way to extend C drive
❌ Why Disk Management Fails in This Case
This is why third-party tools are necessary in this scenario and IM-Magic Partition Resizer is 100% free on Widnows 11-XP. It also has a demo version for Windows Servers and it is called IM-Magic Partition Resizer Server.
Why IM-Magic Partition Resizer? It is 100% free and has roll-back protection feature to fully protect your OS and data from unexpected risks.
Also read: Fix c drive extend volume greyed out or how to move unallocated space next to C drive
If the unallocated space is already located next to the C drive, the extension process is usually straightforward.
Note: Disk Management and Diskpart can only extend C drive when the unallocated space is right next to the C drive under the conditions that the C drive is NTFS and the max capacity is 2TB for MBR disk.
If Disk Management fails, advanced users can try DiskPart to extend the volume manually. Or you may use IM-Magic Partition Resizer when Diskpart and Disk Management fail.
Note: DiskPart has almost the same limitations as Disk Management regarding the conditions for extending a drive.
Many computers include a hidden recovery partition after the C drive. This partition blocks unallocated space and disables the Extend Volume option. Some computers have an EFI partition after the C drive.
Both Recovery and EFI partition cannot be moved by Windows built-in tools like Disk Management or Diskpart, only Partition Resizer can move them.
Do not delete the recovery partition unless you fully understand the risks. The safest solution is to move it using partition software like IM-Magic Partition Resizer.
Also read: How to move the recovery partition or How to move EFI partition
MBR disks have a maximum size limit of 2TB. If the disk reaches this limit, extending the C drive becomes impossible.
Note: MBR2GPT is provided by Windows and it can convert OS disk to GPT under certain conditions.
Details: How to convert disk from MBR to GPT
Windows can only extend partitions formatted as NTFS. If the C drive uses FAT32, Extend Volume will remain unavailable.
Note: There is no way to convert the C drive from FAT32 to NTFS. You may use free tool IM-Magic Partition Resizer to directly extend the FAT32 C drive instead of changing it to NTFS.
The following command will not work.
If you have seen the above steps somewhere else, you may find they will not work.
Why is Extend Volume greyed out even when unallocated space exists?
Because Windows requires the unallocated space to be directly next to the C drive. If another partition blocks it, the option is disabled.
What is the easiest way to fix Extend Volume greyed out?
The easiest and safest way is to move the unallocated space next to the C drive using free partition software like IM-Magic Partition Resizer, then extend the C drive.
Is it safe to extend the C drive?
Yes. When performed correctly with backups, extending the C drive is safe and common. IM-Magic Partition Resizer offers rollback protection during disk partition resizing, keeping the OS and data fully protected from unexpected events.
If you are facing the Extend Volume greyed out issue, the problem is almost always related to disk layout limitations rather than missing space. Resize-C recommends identifying your specific case first and applying the correct solution to safely add unallocated space to the C drive.