How to Extend C Drive in Windows 10? [3 Efficient Ways]

Quick Fix:

How do you extend C drive? To extend your C drive, you'll need to use the Disk Management tool in Windows. 

• If there is unallocated space right behind the C drive, you can right-click the C drive, select Extend Volume, and follow the extending wizard to finish the process.
• However, if there is no unallocated space right behind the C drive, you will need to delete another partition right behind the C drive (like D) and then extend the C drive with the freed-up space. 

Here's a step-by-step guide:

1. Open Disk Management: Right-click on the Start menu and select "Disk Management". 
2. Delete a Partition: Right-click on the partition right behind the C drive and select "Delete Volume." You can see there is unallocated space behind the C drive.
3. Extend C Drive: Right-click on the C drive and select "Extend Volume." 
4. Follow the Wizard: The Extend Volume Wizard will guide you through adding the unallocated space to your C drive. 
5. Finish: Click "Finish" to complete the process. 

If you don't want to lose data, you need to back up your data in advance or use third-party partition management software to manage your disk space.

When the C drive (system partition) is out of space, the C drive is full, or you get a low disk space warning on Windows 10, and hardware upgrades become unavailable. Here is a real case from Microsoft Community:

Continue to read and learn why the Extend Volume option greyed out and how to extend the C drive in Windows.

How to Extend C Drive 

You may be wondering how to extend the C drive in Windows 10 for now. EaseUS will introduce how to extend partitions, especially to successfully increase the volume of the C drive in Windows 10. 

• If there is unallocated space right behind C drive, Disk Management can efficiently extend C drive; for experienced users, DiskPart is even a faster option to increase C drive space.

• However, if there is a recovery partition or another partition between the C drive and the unallocated space, Disk Management and DiskPart don't work. To break the limit, you need to turn to EaseUS Partition Master.

Check the table below and select a suitable way. 

Based on your case, follow the instructions below to increase the C drive space.

Way 1. EaseUS Partition Master

For users who want to extend the C drive with a professional and easy method, EaseUS Partition Master Professional is the right choice. As a magic partition software, EaseUS Partition Master supports extending the C drive with non-adjacent/adjacent unallocated space. Also, it can directly allocate free space to C drive from another partition. Its clear interface makes it easy to use. There are several guides for you.

1. Guide 1. Extend C Drive with Nonadjacent/Adjacent Unallocated Space
2. Guide 2. Smart Extend C Drive with Low Disk Space Warning
3. Guide 3. Allocate Free Space to C (No Unallocated Space)

Now, let's select a suitable guide and get started.

Way 1. Extend C Drive in Windows 10 Nonadjacent/Adjacent Unallocated Space

• Difficulty Level: Easiest
• Suitable for: Windows beginners and professionals
• Apply to: There is adjacent or nonadjacent unallocated space on the same disk.

Your data is completely protected during all operations. Let's see how to extend the volume of C drive in Windows 10 here:

Extend System C drive with unallocated space

1. 1. Right-click on the System C: drive and select "Resize/Move".
2. 2. Drag the system partition end into the unallocated space so to add it to the C: drive. And click "OK". 
3. 3. Click "Execute Task" and "Apply" to execute the operations and extend the C drive.

1. The program may pop up a window to ask you to restart your computer after executing the operation and do as the software requires.
2. Your computer will restart with a bigger system C drive and better computer performance on your Windows 11/10 PC.

Experiencing unexpected issues? Our dedicated troubleshooting team can help you navigate any obstacles you encounter.

Guide 2. Smart Extend C Drive with Low Disk Space Warning

As a professional disk management software, EaseUS Partition Master can automatically detect the status of the C drive, and when you hover the mouse over the C drive, it will offer "Adjust with one click" to extend the C drive and solve the C drive low disk space error.

• Data Loss: No
• Pros: One click to increase C drive space on Windows 10

Step 1. Click "Adjust with 1-Click" to extend C drive.

When your C drive is out of space, hover your mouse over the C drive, you will see the Low Disk Space alert on EaseUS Partition Master. Click "Adjust with 1-Click" to extend it.

Step 2. Click "OK" to extend C drive automatically.

By clicking "OK", EaseUS Partition Master will automatically allocate space to your C drive to solve the low space issue.

Extra Option: You can also click "Manual Adjustment" to extend the C drive manually.

When turning to Manual Adjustment, select the C drive, and drag dots rightward to add more space to C drive. Click "OK" to confirm.

Step 3. Confirm to resolve low disk space in C drive

Click the "Execute Task" button at the top corner and start all pending operations by clicking "Apply".

Do you see? This tool can help extend system partition in Windows 10 efficiently. Share this article to let more users know about this tool.

Guide 3. Allocate Free Space to C (No Unallocated Space)

This method applies to cases where the C drive is out of space while another partition has much free space. To extend the C drive, EaseUS Partition Master can allocate space from another partition to C.

• Data loss: No
• Apply to: There is no unallocated space, but D drive or another drive has much free space to use
• Operation difficulty: Easy for beginners

Here is how: （I set D as an example. Here is how to allocate free space form D to C.)

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

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

If you only have one system C drive on the disk, and it's full now, but you get a second drive with huge free space, relax. You can apply EaseUS Partition Master with its Extend with Data Migration feature for help. You may follow this guide for help:

Aside from assisting you in extending system partition, this software lets you enjoy all the powerful functions, such as:

• Move space from D to C
• Extend System Partition in Windows 11/10
• How to Fix Cannot Extend Volume

Way 2. Disk Management

• Premise: There must be unallocated space right behind the C drive.
• Difficulty Level: Medium
• Suitable for: Windows-experienced users

Notice:

It's always a good idea to back up your important data before making any changes to your disk partitions. 

You can use Disk Management to extend C drive on Windows 10, but there must be unallocated space behind the C drive. Otherwise, you might find that the Extend Volume is greyed out and unavailable.

Check if you have contiguous unallocated space next to the C drive, as the picture shows.

Here is how to extend the C drive in Windows 10 using Disk Management:

Step 1. Press the Windows + R keys simultaneously to open the Run dialog.

Step 2. Type diskmgmt.msc and hit Enter to open the Disk Management utility.

You can also right-click This PC and choose "Manage -> Storage -> Disk Management".

Step 3. Right-click on the C drive and choose "Extend Volume".

Step 4. Set and add more size to the C drive and click "Next" to continue. 

Step 5. Click "Finish" to complete the process.

Note that if the unallocated space is not behind the C drive, you can revert to Method 1 and apply EaseUS Partition Master for help. 

Way 3. DiskPart

• Premise: There must be unallocated space right behind the C drive.
• Difficulty Level: Medium
• Suitable for: Windows experienced users and professionals

Notice:

It's always a good idea to back up your important data before making any changes to your disk partitions. 

There is another tool named Diskpart, which also enables you to manage your local disk and partition. The Windows Command Prompt utility works the same as the Disk Management tool. One important point is that inexperienced users should not rush to this method because a tiny mistake can damage the entire hard drive. To do so, you'll also need to create unallocated space next to the C drive, then follow these steps below to extend the volume of the C drive using CMD with contiguous unallocated space:

Step 1. Press the Windows + X keys and choose "Command Prompt (Admin)".

Step 2. Type the following commands, and each one ends with the "Enter" key:

diskpart
list volume
select volume x (x is the C drive number)
extend size =number (the number is the MB size for extending the C drive)

Why Can't I Extend the C Drive?

Some users report that even if unallocated space exists, Windows still prevents them from extending the C: drive. Here are the most common reasons:

🔹1. Unallocated Space Is Not Adjacent to C: Drive Windows

Disk Management only allows extending a partition into immediately adjacent unallocated space on its right.

• 💡 Tip: If there's a partition (like D: or Recovery) between C: and the unallocated space, the "Extend Volume" option will be greyed out.

🔹 2. A Recovery or System Partition Is Blocking the Way

A small system or recovery partition may exist between the C: drive and the unallocated space. This prevents Disk Management from extending C drive.

• ⚠️ Warning: Deleting a recovery partition may remove your system restore options or factory reset tools.

🔹 3. System Drive Protection or Volume Lock

System partitions like C: are often protected while Windows is running. Sometimes, Windows locks the volume due to background tasks, updates, or pending reboots.

• 🔒 Note: Even if space is adjacent, the system might not allow modification while Windows is active.

🔹 4. Disk Is Using the MBR Partitioning Scheme

MBR (Master Boot Record) has several limitations: Only four primary partitions are allowed, and the maximum partition size is 2 TB

🔹 5. File System or Disk Errors

Corruption or logical errors on the disk may prevent changes to the partition layout.

Share this post and let more users know how to extend the C drive and why they can't extend the C drive in Disk Management.

Bonus Tip: Upgrade Windows 10 OS Disk to a Larger Disk

Clone and replacing the old drive with a bigger one can also solve your problem. To do so, you have two options:

#1. Migrate Windows 10 to a New HDD/SSD without OS Reinstallation

If you don't want to migrate other data on the C drive, you can only migrate the Windows operating system to a new drive with the help of EaseUS Partition Master. 

Video Tutorial: How to Migrate OS from HDD to SSD

#2. Upgrade C Drive to a Bigger HDD/SSD

If you want to replace the whole C drive, both the system and the data, clone this drive with the help of EaseUS Partition Master. This feature lets you move your system and data to SSD/HDD easily and quickly. Follow the steps below to clone your drive:

Step 1. Select the source disk.

• Click the "Clone" from the left menu. Select the "Clone OS Disk" or "Clone Data Disk"  and click "Next".
• Choose the source disk and click "Next".

Step 2. Select the target disk.

• Choose the wanted HDD/SSD as your destination and click "Next" to continue.
• Read Warning message and confirm "Yes" button.

Step 3. View the disk layout and edit the target disk partition size. 

Then click "Continue" when the program warns it will wipe out all data on the target disk. (If you have valuable data on the target disk, back up it in advance.)

You can select "Autofit the disk", "Clone as the source" or "Edit disk layout" to customize your disk layout. (Select the last one if you want to leave more space for C drive.)

Step 4. Click "Start" to start the disk cloning process.

Other Tips to Extend the Volume of C Drive in Windows 10

In addition to these solutions, you may ask about a way to extend the volume of the C drive in Windows 10 with or without software. Here, you can learn other tips to reduce the possibility of a full C drive and resize the C drive.

• Separate OS and personal data: move personal data to a non-system partition.
• Merge partition to C drive: merge used or empty partition to C drive.
• Run Disk Cleanup: clean up junk and temporary files to free up space in the C drive.
• Empty recycle bin: The recycle bin content takes up C drive space, and emptying the recycle bin can increase disk space a bit.
• Move the program to another drive: Transferring programs from the C drive to the D drive or other partitions also helps free up space on the C drive.

Conclusion

In this article, we discussed how to extend the C drive in three reliable ways. After that, we also provided a bonus tip and practical tips to help users increase the volume of the C drive in Windows 10. If you want to resize your system partition, download EaseUS Partition Master and follow the mentioned methods.

Related FAQ on How to Extend C Drive in Windows 10

In addition to extending the C drive, some people have asked related questions. Here are some examples:

1. Can we extend the C drive?

Yes, you can. You can use the third-party software, Disk Management or Diskpart to expand your C drive in Windows 11/10 easily. Among them, EaseUS partition software is my recommendation. It can extend any drive easily and quickly.

2. Can I extend C drive from D?

Yes, sure. You can extend the C drive from the D drive using the unused free space. Here is how to do so:

• Open Disk Management, right-click on the D drive, and select "Shrink Volume."
• Set the size of unallocated space you want to shrink from the D drive and click "Shrink."
• Click "OK".
• Right-click on the C drive and select "Extend Volume".
• Select to add the created unallocated space to the D drive, and click "OK."

3. Why extend the volume grayed out windows 11/10/8.1/7?

When you are using Disk Management to increase C drive space, you can right-click "Computer" and choose "Manage" to go, then you can enter "Disk Management." If you see the Extend Volume option grayed out on your computer, there is no unallocated space on your hard disk.

4. How do you add space to the C drive?

• Launch EaseUS Partition Master.
• Right-click on the System C: drive and select "Resize/Move."
• Drag the system partition end into the unallocated space.
• Click "Apply" to execute the changes and extend the C drive.