How to Change Partition Size Safely in Windows Server 2012?

In this post, you will learn how to change partition size in Windows Server 2012 easily and safely. Two tools will be introduced to help you reduce or increase drive size on Server 2012, 2016, 2019 or the newest 2022.


By Cherry / Updated on May 12, 2023

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When to change partition size in Windows Server 2012?

Changing partition size does not only mean increasing partition size, but also mean reducing partition size. In different situations, you need to make different operation (increase or decrease partition size) in Windows Server 2012.

When one of your hard drives (especially the system C drive) is too small or filled with all types of applications, the "low disk space" warning will keep popping out at the right down corner. As a result, the Windows Server 2012 may run slower and slower; some applications can be even frozen, then what you can do the best is to extend the partition size instead of cleaning up hard drive.

However, when some partitions on your disk are too bigger and only a little space has been used (lots of space are unused), you might be eager to reduce the partition size to make them smaller and create a new partition on the unoccupied space for other purposes.

How to adjust partition size in Windows Server 2012?

When it comes to changing partition size on Server 2012, there are 2 options: Windows built-in Disk Management and third party partition software.

Option 1. Change partition size with Server 2012 Disk Management

Disk Management is a Windows native tool on Windows Server 2012 and other operating systems. It has the "Extend Volume" and "Shrink Volume" features for Windows Server 2012 users to change partition size. With those two functions, you can shrink and extend a partition in few steps.

✪To reduce partition size

Step 1. Press Windows+R on your keyboard to open Run dialogue, input “diskmgmt.msc” and press Enter to open Disk Management window.

Step 2. Right click the partition you want to decrease and select "Shrink Volume".

Shrink Volume Dm

Step 3. Enter the amount of space (1024MB=1GB) and click "Shrink" to execute the operation.

Shrink Size

In a while, this selected drive will be shrunk to the desired size.

✪To increase partition size

Step 1. Right click the NTFS partition that has right adjacent unallocated space and select "Extend Volume".

Extend C Drive

Step 2. Click"Next" in the pop-up Extend Volume Wizard window.

Step 3. Click "Next" to select disk and space, or keep the defaults.

Step 4. Click "Finish" to execute.


Restrictions of Disk Management:✎...
Only NTFS partition can be shrunk and extended. FAT32 and other types of partition are not supported.
Unallocated space can only be generated on the right side of the partition you just shrank.
To extend a volume, there must be adjacent unallocated space on its right side. Otherwise, you may have to delete the partition behind the to-be-extended partition.
In a few cases, you can only shrink little space because there are some unmovable files on the partition, even if there is large amount of free space in the volume.

Option 2. Change partition size with partition manager

From above, we know that Disk Management is not versatile enough when it comes to resizing partitions in Windows Server 2012. So you might want to use a much more powerful partition manager like AOMEI Partition Assistant Server. It can resize partition on Windows Server 2012 (R2) more flexibly with the following advantages:

Supports resizing (increasing or reducing) NTFS and FAT32 partition size as well as encrypted partitions in Windows Server 2012.
Supports moving partition which locates between the partition you want to extend and the unallocated free space. Then the unallocated space can be adjacent behind the partition which needs to be extended.
Enables you to directly merge unallocated space into a partition no matter where it is on the same disk.

What’s more, AOMEI Partition Assistant Server is compatible with Windows Server 2003, 2008 (R2), 2016, 2019, 2022 Windows SBS and all Windows PC OSes, not only just Windows Server 2012. Its "Resize/Move Partition" can help shrink or increase partition size. You can drag the partition towards to left side to reduce the partition size, or towards to the right side to increase partition size if there is adjacent unallocated space. (There is a demo version for a free try.) 

Download Free DemoWin Server & PC
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Resize A Partition

Move And Resize Partition

Besides this feature, the AOMEI Partition Assistant Server provides "Merge Partitions" and "Allocate Free Space" to help change partition size in Windows Server. The "Merge Partitions" is able to merge two ajdacent partitions into one without losing any data, or merge unallocated space into another partition (no matter whether they are adjacent or not). Take the following steps to increase C drive size in Windows Server 2012:

Step 1. Run AOMEI Partition Assistant Server, right-click the partition and choose "Merge Partitions".

Merge Partitions

Step 2. Tick the unallocated space or another adjacent partition and click on "OK".

Tick Unallocated Space

Step 3. Click on "Apply" and "Proceed" to commit the pending operation.


If there is not unallocated space on the hard drive, you can turn to "Allocate Free Space", which is able to directly transfer some unused free space from one drive to another within 3 steps: Right click the partition that has enough free space and select "Allocate Free Space"from the drop-down menu. In the next window, input how much space you want to transfer to the target drive and choose the target partition, click on "OK", and then click “Apply” and “Proceed”.

Allocate From D to C


AOMEI Partition Assistant Server permits you to change partition size in Windows Server 2012 (R2) more easily than Disk Management. Besides adjusting partition size on Windows Server 2012 (R2), it can do more for Windows Server, such as migrating OS to SSD or HDD, converting disk between MBR and GPT partition styles, making WinPE bootable CD/USB, etc.

If you want to use AOMEI Partition Assistant on unlimited PCs and servers within your company, please choose Unlimited Edition; if you want to make a profit by providing technical services to your clients, please choose Technician Edition.

Cherry · Staff Editor
Cherry is an editor of AOMEI Technology, she covers backup & restore, hard disk & partitions management, cloud files transfer, website & database backup and so on for AOMEI. She enjoys helping people find solutions to their problems. She loves traveling, cooking, reading and so on. She takes most of time with her family when she is not working.