By Cherry / Last Updated October 13, 2021

Need to add unallocated space to C drive in Server 2016

Many Windows Server 2016 users may find that the system partition is too small to hold system and related files and want to add unallocated space to extend system partition. Besides, some users plan to extend the system partition just in case that the C drive is running out of space, because that may lead the whole system and all the applications loading slow. But how to add unallocated space in Windows Server 2016?

Fortunately, this article provides you with three ways to add unallocated space to C partition for extending system partition under Windows Server 2016.

3 Ways to add unallocated space to C drive in Windows Server 2016

Now, you can check out the 3 ways, in which you can merge unallocated space to C drive or other small partitions in Windows Server 2016. Afterward, you can choose the best way based on your requirements.

Way 1. Add unallocated space with Server 2016 Disk Management

In Windows Server 2016 Disk Management console, you can do basic management to create partitions, format, delete, shrink as well as extend partition. The “Extend Volume” function can help add the unallocated space into a partition. But it has a key limitation: the unallocated space can only be added into its left adjacent partition.

If the unallocated space is adjacent to C drive or other partition you want to extend, you can follow the steps to add unallocated space in Windows Server 2016.

Step 1. Press WIN+R and type “diskmgmt.msc” and press Enter to open Server 2016 Disk Management, right click the system partition, select “Extend Volume”.

Extend Volume Server 2016

Step 2. In the pop-up window, type the amount of Unallocated space and click ”Next”.

Extend Size Server 2016

Step 3. Confirm the operation and click “Finish” to proceed. Then the unallocated space will be added into system drive.

Extend Finish Server 2016

However, unfortunately, if the unallocated space is not adjacent to the partition, the Extend Volume should be grayed out, and you cannot use the Disk Management to add unallocated space to Windows Server 2016.

Extend Volume Greyed Out Server 2016

As a workaround, you can delete the partition behind C: partition and adjacent to C: partition (like D: partition) first to create contiguous unallocated space and then add it to the system drive. But that may cause data loss on the deleted partition.

Way 2. Add unallocated space to C drive using Diskpart

Diskpart is another utility of Windows Server 2016 for managing disk partitions. Different from Disk Management, it uses syntax with the command line. To extend system partition for Windows Server 2016, you can use the following syntax:

  • list disk

  • select disk 0

  • list volume

  • select volume

  • extend size=

Take extending system partition on disk 0 as the following screenshot shows:

Diskpart Extend Volume

However, Diskpart has limitations when adding unallocated space into partition for extending. For example, if there is another drive between C drive and the unallocated space, the extend command is invalid, same as Disk Management. Besides, both DiskPart and Disk Management can only extend NTFS partition.

So, what should you do if those two methods cannot add the unallocated space in Windows Server 2016? It’s time to go for Method 3.

Way 3. Add unallocated space with Server partition software

Because of the limitations, DiskPart command and Disk Management are not the best tools to add unallocated space into (C) partition in Windows Server 2016. To do this, professional Server partition software is a better choice. Here we recommend using AOMEI Partition Assistant Server. It is a great disk manager for Windows Server 2022/2019/2016/2012 (R2)/2008(R2)/2003 and Windows 10/8/7.

When you cannot add unallocated space into C drive or other target partitions because they are not adjacent, you can use its “Move Partition” function to move the unallocate space behind the to-be-extended partition. Moreover, its “Merge Partition” can directly merge unallocated space into partition regardless of the location of unallocated space. Here we take “Merge Partition” as an example as it is more conveniently.

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Step 1. Download AOMEI Partition Assistant Server trail, install and launch it. You will see the main environment of your disks. And you can see the unallocated space is at the end of the disk. Right click C: partition, select “Merge Partitions”.

Merge Partition

Step 2. In the pop-up window, tick the uanllocated space and click “OK”.

Choose Unallocated Space

Step 3. Back to the main interface, click “Apply” at the toolbar to submit all the operations. It will layout all the operations and you can confirm it, with no problem, click “Proceed” to go on, and wait till it finished.

Apply Proceed

That’s all. it is easy to add the unallocated space to partition in Windows Server 2016 with AOMEI Partition Assistant Server. Actually, you can also use the Extend Partition Wizard to extend size for Windows Server 2016.


So, if the unallocated space is right adjacent to the partition you need to expand, the first two ways are great enough. If not, AOMEI Partition Assistant Server can help add unallocated space in Windows Server 2016 easily. No matter which situation you are in, you can get it done easily.

Apart from extending partition with unallocated space, AOMEI Partition Assistant Server also has other fantastic features like converting MBR to GPT without deleting partition (the versa is also true), moving Windows Server to new hard drive, splitting partition, cloning partition, cloning disk etc.

There is an AOMEI Partition Assistant Unlimited Edition for you if you want unlimited usage within one company. And a great function, "Create Portable Version" is available in AOMEI Partition Assistant Unlimited. The function enables users to create AOMEI Partition Assistant to a removable device so that users can directly run it on target computers without installation.