By AOMEI / Last Updated May 15, 2020

When do you need to migrate MBR OS to GPT disk?

If you want to replace your old hard drive with a much larger one that has more than 2TB capacity, there are a few things you need to take into consideration. Usually, old hard disk drives (HDD) are initialized as MBR disk, which does not support anything more than 2TB. Therefore, in order to use a HDD beyond 2TB, it has to be GPT disk. For that, you need to check if your BIOS supports UEFI. If it does, you can Migrate OS from MBR to GPT disk without reinstalling Windows. Is there any tool that can do this without losing usable disk space?

SSD migration tool – AOMEI Partition Assistant

Unlike most of other data migration software, AOMEI Partition Assistant will not convert the destination disk to MBR while migrating OS from MBR to GPT. It can directly transfer MBR OS to GPT disk and it will create an EFI partition and MSR partition so that the cloned GPT disk becomes bootable after the migration. Of course, as you may know, you need to make sure the UEFI boot mode is enabled in BIOS before you can boot from the GPT disk. What’s more, it allows you to adjust the partition size on the destination HDD before or after the migration starts.

How to migrate system MBR to GPT

Install your GPT disk in your computer or connect it with a SATA-to-USB adaptor and then you can use this software to migrate OS.

Step1. Download and run AOMEI Partition Assistant.

Step2. In the main interface, you can see all the partitions and disks available. Make sure the GPT disk has some unallocated space. If it does not, you can shrink or delete partitions on SSD to generate some unallocated space. Then select the option “Migrate OS to SSD”.

Migrate OS

Step3. In the next pop up window, select the unallocated space on the SSD as destination location.

Select Disk Space

Step4. In the next screen, you can adjust the partition size on the SSD if needed and then click “Next”. You can also resize system partition after the migration without data loss.

Resize Partition

Step5. Preview the partition layout and click Apply to apply all operations if no problem.


The process will be complete under “AOMEI Pre-OS mode”, which will restart your computer, so save everything you are editing before the migration. After you migrate MBR OS to GPT disk, make sure you have enabled UEFI boot mode in BIOS before trying to boot the GPT disk. Additionally, AOMEI Partition Assistant allows you to do MBR to GPT conversion without data loss, and vice versa, so you can also convert your MBR disk to GPT before system migration.