By Bryce / Last Updated June 28, 2020

Content
1. Why increase partition capacity?
2. Step-by-step guide: Increase partition capacity in Windows
2.1 Extend partition via Disk Management
2.2 Increase partition size via Diskpart
2.3 Merge Partition with unallocated space
2.4 Allocate free space from one partition to another

Why increase partition capacity?

“My Windows 10 computer tells me that I’m running out of the space on C drive and I can free up space by deleting old files. I don’t want to remove files. The hard drive has two partitions: C and D; and D has lot of unused space. How can I increase C drive space?”

As aforementioned, if you find that a certain partition has not enough space to contain more and more data, you can increase the partition size. And you enlarge a partition as you don’t want to waste the unallocated space forming after deleting recovery partition or cloning to a larger disk.

Step-by-step guide: Increase partition capacity in Windows

When you need to increase partition capacity of C drive or other drives, you may be in different conditions:

▪ Condition 1. There is unallocated space contiguously behind the partition that you want to extend on the same hard drive.
▪ Condition 2. The unallocated space is behind the partition that you want to extend and there is a partition between them.
▪ Condition 3. The unallocated space is before the partition that is going to be extended.
▪ Condition 4. There is no unallocated space on the hard drive that contains the partition that you need to enlarge.

If you are in condition 1, you can easily increase partition size within Disk management or Diskpart.

✔ Extend partition via Disk Management

Step 1. Press Windows + R at the same time, type “diskmgmt.msc” and hit Enter.

Step 2. In Disk Management, locate the partition whose capacity needs to be increased, right-click it and choose “Extend Volume”.

Extend Volume

Step 3. You’ll be in "Extend Volume Wizard" interface, click “Next” to continue.

Extend Volume Wizard

Step 4. Here Disk 0 is automatically selected as the disk from which you take free space to C drive. Click “Next“

Extend Volume Wizard Select Disks

Note: Supposed that if there is another hard disk that owns unallocated space, you can’t add the unallocated space to C drive as a basic disk can’t own space on two or multiple partitions. If you want to extend partition with unallocated space on different disk, you can convert basic disk to dynamic at first.

Step 5. Confirm the operation and then click "Finish". After a while, you’ll find that the partition extended.

✔ Increase partition space via Diskpart

Step 1. Press Windows + R simultaneously, input “diskpart” and hit Enter.

Step 2. Run commands listed as follows:

  • list disk – all disks will be listed

  • select disk n – n means the disk number of the disk that contains the partition that you want to extend

  • list partition – all partitions on the selected disk will be displayed

  • select partition m – m is the partition number of the partition that you want to enlarges

  • extend

Diskpart Extend Partition

PS.: If you want to add a specified size of unallocated space to partition, you can replace “extend” with “extend size=x”, where x is the size in MB that you want to add to the partition.

When you are in condition 2/3/4 (there is no contiguous unallocated space behind the partition that you want to extend), you can’t increase partition size through the same steps in condition. Otherwise, you can find that the Extend Volume option greyed out or receive an error saying “There is not enough usable free space on specific disk(s) to extend the volume”.

But don’t worry, a powerful third-party partition manager, AOMEI Partition Assistant Professional can be a great solution! With “Merge Partitions” function, it enables you to increase partition size by adding unallocated space that is or isn’t contiguously behind the partition that you want to enlarge. With “Allocate Free Space” function, it helps you to take free space from one partition to another partition without data loss. If you are in condition 2/3, you can increase partition capacity via “Merge partitions”; if you are in condition, choose “Allocate Free Space” function. Then, have a look at how to use the great partition manager to enlarge partition effortlessly.

☞ Note: You can download its demo version to have a try at first!

✔ Merge Partition with unallocated space

Step 1. Install and run the partition manager. In the main interface, right-click the partition that you want to enlarge (here is partition C) and choose “Merge Partitions”

Merge Partitions

Step 2. In this window, check the box before Unallocated and click "Next".

Add Unallocated Space To C Drive

Step 3. Here you can see that the capacity of partition C will be increased. Click "Apply" and "Proceed" to commit the operation.

Apply Merge

✔ Allocate free space from one partition to another

Step 1. Right-click the partition that has enough unused space and choose “Allocate Free Space”.

Allocate Free Space

Step 2. In the pop-up dialogue, type the size and choose your destination partition.

Allocate From D To C

Step 3. Here you can preview the result. After confirmation, click "Apply" and "Proceed" to execute it.

Apply Allocate Free Space

✍ Notes:
◆ Apart from increasing partition capacity, the partition manager can help you complete many operations, such as converting disk from MBR to GPT without deleting partitions and splitting partition easily.
◆ AOMEI Partition Assistant Professional is for Windows 10/8.1/8/7, XP, and Vista. To enlarge partition in Windows Server 2019/2016/2012(R2)/2008(R2)/2003, please employ AOMEI Partition Assistant Server.