Convert MBR to GPT in Windows Server 2012 (R2) without Data Loss

March 2, 2018

Converting MBR to GPT in Server 2012, 2003, 2008 is a simple task. However, when “Convert to GPT Disk” option grayed out, it may become difficult. This article analyzes the reason and offers a workaround.

MBR and GPT in Windows Server 2012

MBR and GPT are different partition styles used on hard drives. Master boot record (MBR) disks use the standard BIOS partition table. GUID partition table (GPT) disks use unified extensible firmware interface (UEFI).When you plug in a new hard drive in Windows for the first time, it will ask you to initialize the hard drive to MBR or GPT. In general, if the hard drive is less than 2TB, it is suggested to initialize to MBR. Otherwise, initialize to GPT. From here you can see, MBR partition table has 2TB capacity limitation. Converting between MBR and GPT is available.

Another obvious drawback of MBR is you can only create four primary partitions or three primary partitions plus one extended partition on this table. GPT has no limit in this aspect and it allows you to create up to 128 primary partitions. So when hard drive capacity has been expanded, some users need to convert MBR to GPT Server 2012 to fully take advantage of the disk.

Convert MBR to GPT in Server 2012 with built-in tools

Windows Server 2012 provides snap-in tools that can help you do the conversion, if the need ever arises. They are graphical user-interface Disk Management and Diskpart in CMD. There is one point need to be paid attention to when using these two tools: both of them support convert empty disk between MBR and GPT. Disk Management cannot convert running system disk from MBR to GPT in Server 2012, and to convert system disk with Diskpart, an installation disc is necessary.

Convert MBR to GPT in Windows Server 2012 R2 with Disk Management

The quickest way to access Disk Management in Windows Server 2012 is to right-click the bottom-left-corner on the desktop to open Quick Access Menu. Disk Management is listed there. Since it supports convert empty basic disk to GPT, you need to delete all partitions or volumes on the disk, or you’ll find “Convert to GPT Disk grayed out”.

1. Right-click the partition and select “Delete Volume” to delete existing partition on the hard drive you want to convert to GPT in Server 2012. It is advised to backup important data before formatting or deleting.

Delete Volume

2. After deleting all volumes, right-click the disk and select “Convert to GPT Disk”. The conversion will be completed in a short while.

Disk Management Convert to GPT


  • Before you convert disks, close any programs that are running on those disks.

  • You cannot use the GPT partition style on removable media.

As covered before, you cannot convert disk that running Windows Server 2012 to GPT because Windows does not allow you to delete system drive before converting. Therefore, Diskpart plus installation disc combination can be used as a workaround for converting MBR to GPT in Server 2012.

Windows Server 2012 convert MBR to GPT with Diskpart

In the first place, backup files you care most before you do the conversion. Back up entire hard drive to storage that you’ll not convert to GPT, if necessary.

1. Shut down your Server 2012 and insert Windows Server installation disc and boot from the disc.

2. Press <Shift> + <F10> key combo to open Diskpart utility. Now, input below commands in Command Prompt to convert to GPT disk:

  • list disk

  • select disk n (n stands for the number of the disk need converting to GPT)

  • clean

  • convert gpt

  • exit

Diskpart Convert GPT

Note: all data will be wiped out after this conversion. If backed up before, backup images can be restored now. Diskpart can also be used to convert data disk to GPT under Windows environment.

As simple as they are, these tools have risk to cause data loss. Backup and restore increase time and effort cost. What’s more, if there is no Windows Server installation disc around, there is no way to convert system disk to GPT. Under such circumstances, it is a wise move to seek help from third-party software.

Software to convert MBR to GPT in Server 2012 without data loss

AOMEI Partition Assistant Server is professional hard drive partition manager that especially designed for Windows Server OS including Server 2012, Server 2003, Server 2008 and latest Server 2016. It offers technology that can assist you convert MBR to GPT in Server 2012 (R2) without deleting or formatting partitions or volumes. In other words, you can preserve system files and personal data on disk while converting to GPT.

Moreover, after converting to GPT, the unallocated space at the end of the disk can be allocated to any existing partitions with the help of AOMEI Partition Assistant. Converting from GPT to MBR is also workable with this software. It has a user-friendly interface that is suitable for both computer experts and novices. Why don’t you download this software and have a try?

How to convert MBR to GPT in Server 2012 without deleting?

Step 1: install and start AOMEI Partition Assistant Server. At the main interface, right-click the disk you want to convert to GPT in Server 2012 and select “Convert to GPT Disk”.

Convert Server 2012 to GPT Disk

Step 2: then click “OK”>“Yes” to confirm the operation.


Step 3: click “Apply” and then “Proceed” to commit the task.



  • A reboot is required for this conversion.

  • It is important to backup file you cares most because data loss may be caused by inappropriate operations.


Apparently, there are many ways to convert MBR to GPT in Server 2012/2016/2008/2003, yet to find the easiest way to convert system disk to GPT without data loss is not an easy way. AOMEI Partition Assistant makes up for the disadvantage of Windows Server 2012 built-in tools and does a great job. Except for converting between partition tables, converting between NTFS and FAT32 file systems is also usable.

There is AOMEI Partition Assistant Lite edition that is free to use in Windows Server 2012 which allows you to do basic partition operations and resize and move partition.