How to Change Partition Size in Windows Server 2012 R2

by Jacob, Updated on: September 12, 2026

Many people want to change partition sizes for Windows 2012 server after running it for a period of time. The typical example is that the C drive is getting full. They wonder if it is possible to increase C drive space without reinstalling the operating system, as nobody likes to waste a long time repartitioning and restoring from a backup. Some people want to shrink a large partition to create more volumes or merge 2 partitions. This article introduces how to change partition size in Windows Server 2012 R2 with the built-in Disk Management tool and safe partition software.

Change volume size

1. Change Partition Size in Windows Server 2012 via Disk Management

Starting from Windows Server 2008, Microsoft added new "Shrink Volume" and "Extend Volume" functions in the built-in Disk Management. This native tool is able to change volume size without losing data in most cases. However, both functions have many restrictions. Windows Server 2012 inherited the same functions without any improvement. Therefore, you may encounter problems when you adjust the Server 2012 partition size with this native tool.

How to decrease partition size with Disk Management:

  1. Press Windows and X together on the keyboard and then click Disk Management in the list.
  2. Right click a NTFS partition and select "Shrink Volume".
  3. Enter an amount of space and click "Shrink" button. (If you don't enter an amount, all available free space will be used by default.)

Shrink partition

How to increase partition size in Server 2012 Disk Management:

  1. Transfer all files in the right adjacent partition (e.g., D:) to another location.
  2. Right click it in Disk Management and select "Delete Volume".
  3. Right click the left contiguous partition (such as C:) and select "Extend Volume".
  4. Click "Next" till "Finish" in the pop-up "Extend Volume Wizard" window.

Extend volume disabled

Limitations to change partition size in Windows Server 2012 R2 via Disk Management:

  1. It can only shrink and extend NTFS partitions, any other partitions are not supported.
  2. It can only shrink a partition towards the left and generate unallocated space on the right.
  3. It cannot shrink a partition beyond the point where unmovable files are located.
  4. It can only extend a partition when there is adjacent unallocated space on its right.
  5. On an MBR disk, unallocated space deleted from a primary partition cannot be extended to any logical drive. Free space deleted from a logical drive cannot be extended to any primary partition.

In short, Disk Management can only shrink a NTFS partition to create a new volume, or extend a NTFS partition by deleting the right adjacent volume. If you want to extend a partition by shrinking another one, Disk Management cannot help you. As shown in the screenshot, after shrinking the D: drive, the unallocated space is non-adjacent to the C drive and on the left of the E drive. Therefore, Extend Volume is disabled for both partitions.

Extend volume disabled

To change partition size in Windows Server 2012 R2, disk partition software is a better choice.

2. Adjust Partition Size in Windows Server 2012 with Safe Partition Software

Comparing with Disk Management, NIUBI Partition Editor has many advantages such as:

Better than other disk partition software, NIUBI Partition Editor has innovative technologies to protect your system and data:

  1. Cancel-at-Will - you can safely cancel the ongoing operations at any stage before completion.
  2. Virtual Mode - real disk partitions won't be modified until you click "Apply" to confirm.
  3. Hot Clone - clone disk partitions in Windows for backup, migration, and fast disk swapping.
  4. 1 Second Rollback - automatically reverts disk partitions to their original status in a flash if it detects any error.

Download this tool and you'll see all disk partitions with graphical structure on the right, available operations to the selected disk or partition are listed on the left and by right clicking. In the example below, there are drives C, D, and E, as well as a System Reserved partition on Disk 0. The original D: drive is 70GB and the C: drive is 40GB.

NPE Server

How to change partition size in Windows Server 2012 R2 without losing data:

① Shrink a NTFS or FAT32 partition to make unallocated space. For example: right click D: drive and select "Resize/Move Volume". You have 2 options in the pop-up window.

If you drag the left border to the right, or enter an amount in the box of "Unallocated space before":

Shrink D rightwards

Then unallocated space is made on the left side of D.

unallocated produced

If you drag the right border to the left, or enter an amount in the box of "Unallocated space after":

Shrink D leftwards

Then unallocated space is made on the right side of D.

unallocated generated

② Create a new volume with this unallocated space, or combine it into other partitions. To extend partition, right click C: or E: drive and run "Resize/Move Volume" again.

To extend C drive, drag the right border to the right in the pop-up window.

Drag to extend

Then unallocated space is extended into the C: drive.

C drive extended

To extend E drive, drag the left border to the left in the pop-up window.

Drag to extend

Then unallocated space is extended into the E: drive.

Drive E extended

③ Click "Apply" on top left to confirm and execute.

How to change partition size in Windows Server 2012 R2 without data loss:

Video guide

No partitioning software can extend a volume by taking free space from another separate disk. If there is no available free space on a disk, you need to clone this disk to a larger one and extend partition with extra space. Watch the video

3. Change Virtual Partition Size for RAID Array, VMware, Hyper-V

If you want to resize a RAID partition in Windows Server 2012 R2 and other versions, do not break the array or perform any operations on the RAID controller, just follow the steps above. To the Operating System and NIUBI, there is no difference whether you use a physical hard disk or any type of hardware RAID array.

If you want to change size of virtual partition for Windows 2012 server in VMware or Hyper-V, firstly, check if there is available free space on the same virtual disk. If yes, install NIUBI Partition Editor to the virtual server and follow the steps above. If there's no available free space on the same disk, you can expand the virtual disk without copying to a larger one, and then extend partition with additional disk space.

Besides helping to change partition sizes in Windows Server 2012/2016/2019/2022/2025 and previous Server 2003/2008, NIUBI Partition Editor helps you perform many other disk and partition management operations.

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