How to Add Partition to C Drive in Windows

Do you know how to add partition to C drive in Windows to make additional free space? To save your C drive with insufficient space, this post offers various solutions.


By Lucas / Updated on May 12, 2023

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How can I add partition to C drive in Windows 10?

C drive full

Guess many of you confront this dilemma in your Windows PC. It’s not a big deal but it’s quite annoying because once the C drive is full, many programs won’t run normally and your system might meet other issues like frozen frequently, can’t boot successfully, blue screen…etc.

Various reasons can make this happen. C drive is the default storage drive, if you don’t manually change the storage location to another drive, all things will be stored on C drive, usually in the “Program Files” or “Program Files (x86)” folder.

As the picture shows, although C drive is running out of space, D drive still has sufficient capacity. Thus, some people might ask “Can I add partition to C drive?” Well, Disk Management can do this, but it requires you to delete the next drive to make it unallocated, then you can extend the C drive by adding partition.

How to add partition to C drive in Windows 10/11

Deleting a partition will undoubtedly result in data loss; but, what if the following partition included crucial data files? This method may not be suitable for the majority of users.

Is there a method to add a partition on the C drive without deleting data? Disk Management cannot accomplish this; however, AOMEI Partition Assistant Professional can. It is a disk/partition manager for Windows PCs that works with Windows 11/10/8/8.1/7/XP. So, regardless of which system you're using, this tool might be of great assistance.

The “Merge Partition” feature of this tool can merge two normal adjacent partitions into one partition and merge one normal partition with non-continuous unallocated space.

▶ Attention:
The data on the two partitions is totally safe. The data on that partition will be stored in a folder named the drive letter. For instance, if you merge the D drive to the C drive, the data on the D drive will be stored on the C drive in a folder called “D (drive)”.

All of the details are shown in the following.

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1. Merge two normal partitions into one

Step 1. Download and launch AOMEI Partition Assistant. Right-click the C drive, and select "Advanced"> "Merge Partitions" in the menu.

Merge partition

Step 2. In the pop-up window, tick the drive that has sufficient space, here we use the D drive, in the check box, and select the C drive. And then click "OK" to continue.

Tick D drive

Step 3. Please click "Apply" on the toolbar.


2. Merge unallocated partition into a partition

Step1. Launch AOMEI Partition Assistant. In the example, there is an unallocated space after D drive. Right-click the C drive where you want to merge unallocated space to and select "Advanced"> "Merge Partitions" in the menu.

Merge Partition

Step 2. Tick the check box of unallocated space, and then click "OK" to continue.

Tick unallocated space

Step 3. You can preview changes. To save the changes, please click "Apply" on the toolbar.


Note: ◤ If the partition has running applications, AOMEI Partition Assistant will suggest you close them.

Add unallocated space to the C drive without deleting an existing partition

Besides the above method to increase the space of the C drive, this program provides another way for users whose disks don’t have any unallocated partition and who may wish to keep the existing partition.

The “Allocate Free Space” function can share free space from another drive to the C drive. The operations only require a few clicks, all data is safe, nothing will be deleted.

Step 1. Launch AOMEI Partition Assistant, right-click the partition from which you want to allocate free space, and select "Allocate Free Space". Here, we click D drive. 

Allocated free space

Step 2. Now you will see a pop-up window. Type in the size of the free space which you want to cut from the D partition and this free space will be directly added to the C drive.

Allocate space

Step 3. You can see the operation result before confirming the start. Click "Apply" to execute this operation.


When it’s finished, you need to reboot your PC. After that, you successfully add space to the C drive.

◤ Only open space from one partition can be transferred to another. The allotted space should be less than or equal to the amount of vacant space on the source partition.
◤ If there are any other apps active on the partition where you intend to execute the operation, AOMEI Partition Assistant will prompt you to close them by clicking "Retry."


Now you know how to add partition to C drive in Windows. With the help of AOMEI Partition Assistant, disk and partition management will be much easier for any user. This tool also has Server Edition, if your Server device has a crowded C drive, you can also find nice solutions.

Lucas · Staff Editor
I prefer peaceful and quiet life during vacation,but sometimes I watch football match if my favorite club performs brilliantly in that season. And I love reading, painting and calligraphy, thus I send my friends festival handwriting cards every year.