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[2023 Fixes] How to Solve Unable to Extend C Drive

If you are experiencing unable to extend the C drive on your Windows computer, you will find the causes and practical solutions in this article. Read and learn more details.

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Updated by Roxanne on Aug 16, 2023

C drive will be out of space after installing too many programs or updating the Windows system, which is the most common issue in Windows-based computers. To fix this problem, you can use the Windows Disk Management tool to extend the C drive with free space. However, you may find the extend volume option greyed out, and you are unable to extend the C drive.

The reasons why you are unable to extend the C drive vary. Calm down. In this guideline, EaseUS will explain all the potential reasons why this happens and provide five solid methods that apply for different reasons.

How to Fix Unable to Extend C Drive - 5 Methods

Before coming straight to the point, let's look at the overview of these five methods in the following basic information table:

⏱️Duration 5-8 Minutes
💻Goal Solve unable to extend C drive
🧰Required tool

Disk resize tool - EaseUS Partition Master🥇

Windows built-in tool - Disk Management🥈

  1. 1️⃣Allocate Space from Another Drive
  2. 2️⃣Delete Volume to Create Unallocated Space
  3. 3️⃣Resize the C Drive Space
  4. 4️⃣Convert MBR to GPT
  5. 5️⃣Format the Partition to NTFS

When it comes to extending the hard drive, you need to ensure there is enough unallocated space on your target drive. Generally, there are two scenarios:

  • No Unallocated Space: If your C drive has no unallocated space, you can skip to Way 1 and Way 2 to delete volume or allocate unallocated space from another drive.
  • Without Adjacent Unallocated Space: If you already have free space but not next to the C drive, go for Way 3 to learn how to fix it.

Way 1. Allocate Space from Another Drive

EaseUS Partition Master is your most reliable disk space management software, and it can provide multiple solutions to fix the "unable to extend the C drive" issue. If you don't have any unallocated space on your hard drive, you can apply EaseUS Partition Master to extend the partition without unallocated space. With its "Allocate Space" tool, you can easily allocate space from another partition to extend the C drive.

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Follow the simple tutorial to allocate space and extend the C drive:

Step 1. Right-click on the D: partition with enough free space and select "Allocate Space".

Select partition to allocate space

Step 2. Select the target partition - C: drive and drag the partition panel rightward to add the free space from D: drive to C: drive. Then click "OK" to confirm.

Allocate space to extend partition

Step 3. Click the "Execute Task" button and click "Apply" to start the process of moving free space from D: drive to C: drive.

finish extending partition

Way 2. Delete Volume to Create Unallocated Space 

If you prefer Disk Management, you need to remove or shrink the adjacent partition to create unallocated space behind the C drive, which is complicated and tends to lose data. Thus, the first move is to back up your data unless this partition is useless or empty. Below is the full guide on how to delete volume via Disk Management:

Stage 1. Delete volumes to create free space.

  • Press the "Windows + X" keys to launch "Disk Management."
  • Right-click the partition next to the target C drive, choose "Delete Volume," and click "OK."

delete volume on the hard drive

Stage 2. Increase the space of the C drive.

  • Right-click the C drive and select the "Extend Volume" feature to adjust its size.
  • Click "OK" to confirm the process.

choose extend volume

If you have partitions with a lot of space, you can choose to shrink them and make unallocated space referring to the related article:

related articles

How to Shrink Partition in Windows 11/10

This article will introduce three ways of shrinking partitions in Windows 10/11 to cope with the problem of "insufficient unallocated space."

shrink partition in Windows 10/11

Way 3. Resize the C Drive Space

The second situation is that you have unallocated space on the hard drive, but it's not adjacent to the C drive. Windows only allows users to extend a partition with free space next to or behind it. Don't worry. You can retort to EaseUS Partition Master, which has a "Resize/move" tool that can resize the C drive with non-adjacent space.

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Here are the steps on how to resize the C drive space:

Step 1: Locate and select the target drive/partition

Launch EaseUS Partition Master and go to Partition Manager, select the target drive/partition to adjust its size, right-click on it and choose "Resize/Move".

choose the partition

Step 2: Resize or move the partition

1.To shrink the partition, simply drag one of its ends to free up unallocated space. Once done, click "OK". 

drag the mouse leftwards to resize partition

2. To extend the partition, make sure that there is unallocated space aside (if there isn't, follow the above steps to create some). In the same way, drag your mouse into the unallocated space. Click "OK".

drag the mouse leftwards to resize partition

3. To move a partition position, you need to leave unallocated space next to the target partition. If no, free up some unallocated space first.

Right-click the target partition, select "Reize/Move". Then drag the whole partition leftward or rightward to adjust its position. Click "OK" to confirm. 

drag the mouse leftwards to resize partition

Step 3: Confirm the result and apply changes

At this step, you will see the new disk partition information & diagram.

disk partition information after resizing

To save changes, click the "Execute Task" button and then "Apply".

apply changes to the partition

Way 4. Convert MBR to GPT

When your hard drive is initialized as MBR, it will have a 2 TB restriction, and once your partition on the MBR disk reaches 2 TB capacity, the extend volume option will be greyed out and disabled. Thus, you need to convert MBR to GPT before extending the C drive. EaseUS Partition Master will cover you in the disk conversion field and ensure a great experience.

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Check the detailed instructions on how to use the "Disk Converter" of EaseUS Partition Master:

Step 1. Download and launch EaseUS Partition Master on your computer.

Step 2. Go to Disk Converter, select "Convert MBR to GPT" and click "Next" to continue.

convert MBR to GPT - 1

Step 3. Select the target MBR disk that you tend to convert to GPT, and click "Convert" to start the conversion.

convert MBR to GPT - 2

Way 5. Format the Partition to NTFS

Since Windows only supports extending partitions of NTFS or RAW file systems, you need to format your target hard drive if it is a FAT or exFAT file system. Sounds like an exhausting task, so you will need a professional program. EaseUS Partition Master is your best choice for formatting a partition. You also have an extra choice, use the "Resize/move" tool of EaseUS Partition Master as Way 3 to directly extend the C drive since this software breaks the limitation of the file system.

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Refer to the steps below:

Step 1. Right-click the hard drive partition and choose the "Format" option.

Step 2. In the new window, set the Partition label, File system, and Cluster size for the partition, then click "OK".

Step 3. You can see a warning window, click "Yes" to continue.

Step 4. Click the "Execute 1 Task(s)" button, then click "Apply" to start formatting the hard drive partition.

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Why Unable to Extend C Drive?

After solving the "unable to extend the C drive" problem successfully, let's explore what reasons may lead to this issue in detail. Continue to read and view the main reasons listed below to learn why the extend volume option is greyed out in your Disk Management.

  • Without Unallocated Space: To extend a partition with Disk Management, you need to ensure there is enough unallocated space on the target disk.
  • Non-adjacent Unallocated Space: Due to the Windows limitation, Disk Management can only support increasing the partition size with contiguous unallocated space.
  • 2 TB Restriction Of MBR: MBR drive cannot create a partition larger than 2 TB, or the extend volume option will be greyed out. If you format a 4TB hard disk as MBR, you can only use 2TB, and the remaining space will be displayed as Unallocated. All options are grayed out on Disk Management when you right-click this Unallocated space.
  • Only Supported NTFS/Raw File System: Extend Volume in Disk Management is only applicable to RAW or NTFS partitions. Thus, you cannot extend a FAT or other file systems on a Windows system.


When there is no unallocated space or contiguous free space on your hard drive, the extend volume option will become greyed out, and you cannot extend the C drive. Beyond the two reasons, this post also mentioned two more reasons, including the 2 TB restriction of MBR and the incompatible file system. 

Additionally, we offered five helpful ways to fix this problem caused by the four common reasons. As a versatile disk utility, EaseUS Partition Master provides all-around solutions that empower you to break the limitations of Windows and fix the "unable to extend the C drive" issue. Moreover, we prepared some passages that introduce other fantastic features of the EaseUS Partition Master.

FAQs About Unable to Extend C Drive

Now you may have solved unable to extend the C drive problem according to the above-mentioned methods. In this part, we have listed several related questions, and you can check the answers below:

1. How to force extend my C drive?

If your hard disk has insufficient unallocated space, you can allocate space from another drive using a professional drive manager - EaseUS Partition Master. Below is a detailed guide on how to do it:

Step 1. Download this tool, right-click on another partition with enough free space, and select "Allocate Space."

Step 2. Set the target partition as the C drive and drag the partition panel rightward to add the free space from another drive to the C drive. Then click "OK" to confirm.

Step 3. Click the "Execute Task" option and choose "Apply" to start allocating free space.

2. How to extend C drive with my recovery partition?

The recovery partition is the last resort for restoring a crashed computer. So, deleting the recovery partition to extend the C drive is not recommended. Luckily, you can use EaseUS Partition Master to merge non-adjacent space to the C drive. Learn the specific tutorial below:

Step 1. Go to Partition Manager to locate the C drive and apply the "Resize/Move" feature.

Step 2. Drag the partition end to add the unallocated space into the C drive and click "OK" to ensure.

Step 3. Hit the "Execute Task" button and click "Apply" to proceed. 

3. Why my extend volume option is greyed out?

When the Extend Volume option on your computer is grayed out, it's because there is no unallocated space on your hard drive, or no available free space, which means not adjacent to the partition you want to extend. That's why the "Extend Volume" option is disabled and greyed out.

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About the Author

Updated by Roxanne

Roxanne is one of the main contributors to EaseUS and has created multiple posts on digital devices like PCs, Mobile phones, tablets, Mac, etc. She loves to share ideas with people of the same interest.

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