When the C drive (system partition) is out of space, c drive full or you get a low disk space warning on Windows 10, and hardware upgrades become unavailable shown as the next image, what are you going to do? How to extend C drive in Windows 10 could be bothering you for now. Follow the tips below, you'll learn how to extend partition, especially to increase the voluem of C drive in Windows 10 successfully. 

Key Takeawys of How to Extend C Drive in Windows 10:

  1. 1. When you get c drive full error, run antivirus software to clear the virus and remove junk files in the C drive first.
  2. 2. Check if your disk has unallocated space or free space in existing partitions. Follow this guide to extend C drive.

Stay calm if you are experiencing a similar case as a Windows user posted in the Microsoft community, follow the methods below, you'll get efficient methods to enlarge the C drive without causing any boot issue or data loss error. 

How to extend C partition
I've tried disk management but extend option is grayed out.

When I upgraded to windows 10 it split the drives into C and D. The D had files that didn't belong to me, so I deleted them. - from the Microsoft community

Extend C drive

Method 1. Extend C Drive in Windows 10 With EaseUS Partition Manager Software

  • Defficulty Level: Easiest
  • Suitable for: Windows beginners and professionals

For users who want to extend C drive with a professional and easy method, EaseUS Partition Master is the right choice for you. As magic partition software, EaseUS Partition Master is a comprehensive hard disk partition management software that you can't miss.

Also, this software works perfectly with hardware even with RAID and supports all Windows Operating Systems.

Free Download 

Windows 11/10/8/7100% Secure

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

Tutorial 1. Smart Extend C Drive with Low Disk Space Error

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.

How to Adjust Low C Drive Space Step 1

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.

How to Adjust Low C Drive Space Step 2

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.

Manually Adjust Low C Drive Space

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".

How to Adjust Low C Drive Space Step 3

Do you see? This tool can help fix low disk space errors on the C drive efficiently. Share this article to let more users know about this tool.


Tutorial 2. Extend C Drive With or Without Unallocated Space

Option 1. 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.

Option 2. Extend System C drive without unallocated space

  1. 1. Right-click a big partition with enough free space on the system disk, select "Allocate Space".
  2. 2. Select the system drive at the Allocate Space From (*) To section, and drag the end of System C drive into the unallocated space. Click "OK" to confirm.
  3. 3. Click "Execute Task", it will list the pending operations, and click "Apply" to save the changes and extend the C drive.

0:00-0:26 Extend System Drive with Unallocated Space; 0:27-0:58 Extend System Drive without Unallocated Space.

  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.

If you are experiencing a similar issue on Windows 11, Windows 8, or Windows 7, don't worry. Refer to the respective tutorial guide below to increase C drive successfully on your PC:

Bonus Tip: Extend C Drive with Another Hard Drive/SSD

If you only have 1 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 2nd Disk feature for help. You may follow this guide for help:

related articles

How to Extend C Drive with Another Disk?

How to expand C drive from another HDD or SSD? Follow the full guide below, and you'll successfully get rid of the SSD C drive full issue with ease.

Extend C drive with another disk

Aside from assist you extend system partitioin, this software lets you enjoy all the powerful functions, such as:

  1. 1. Move space from D to C
  2. 2. Resize and Move partitions
  3. 3. Copy Partition/Disk
  4. 4. Create, Deleted, and Format partitions
  5. 5. Hide and Unhide partitions
  6. 6. Parttion recovery
  7. 7. Wipe and erase hard drive, etc.

Free Download 

Windows 11/10/8/7100% Secure

Method 2. Extend C Drive in Windows 10 via Disk Management

  • Defficulty Level: Medium
  • Suitable for: Windows experienced users

There must be unallocated space behind the partition which you want to expand with Windows built-in Disk Management utility. Otherwise, you might find that the Extend Volume greyed out and not available.

Asum that you have unallocated space next to the C drive, here is how to extend C drive in Windows 10 using Disk Managemnet:

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

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

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".

extend windows 10 partition

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

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

Extend Windows 10 partition with Disk Managenent

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. 

Free Download 

Windows 11/10/8/7100% Secure

Method 3. Extend Volume of C Drive in Windows 10 via CMD

  • Defficulty Level: Medium
  • Suitable for: Windows experienced users and professionals

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

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

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

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

Extend C drive usign cmd

If there is no unallocated space, you can't extend C drive in Windows 11/10 with this method. Follow and learn how to fix this issue:

related articles

Can't Extend C Drive in Windows 11? Here Is Why and How-to Fix

When you can't extend C drive in Windows 11 or older systems, relax and follow fixes on this page for help.

Image of C drive

Method 4: Upgrade Windows 10 OS Disk to a Larger Hard Drive, No Data Loss

Clone and replace 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 withtout OS Reinstallation

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

Free Download 

Windows 11/10/8/7100% Secure

Video Tutorial: How to Migrate OS from HDD to SSD

#2. Upgrade Windows 10 OS Disk 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 enables you to 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.

Also Read: How to Partition A Hard Drive in Windows 11/10

Tips to Extend the Volume of C Drive in Windows 10 With or Without Software

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

1. Separate OS and personal data: move personal data to a non-system partition.

2. Merge partition to C drive: merge usued or empty partition to C drive.

3. Run Disk Cleanup: cleanup junk files, temprorary files to free up space in C drive.

4. Empty recycle bin: The recycle bin content takes up C drive space and when you empty the recycle bin, you can increase a bit of disk space.

5. Move program to another drive: transfer programs from C to D drive or other partition also helps to free up space on C drive.

Related Questions on Extending 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 Managemen or Diskpart to easily expand your C drive in Windows 11/10. 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 C drive from D drive by using its unused free space. Here is how to do so:

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

3. Why extend 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", choose "Manage" to go, then you can enter "Disk Management". If you see the Extend Volume option grayed out on your computer, it means that there is no unallocated space on your hard disk.

4. How to add space to 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.

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Updated by Tracy King

Tracy became a member of the EaseUS content team in 2013. Being a technical writer for over 10 years, she is enthusiastic about sharing tips to assist readers in resolving complex issues in disk management, file transfer, PC & Mac performance optimization, etc., like an expert.

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