Before figure out how to migrate MBR OS to GPT disk, you should know what is MBR and GPT first.
▶MBR is the abbreviation of Master Boot Record, which allows a maximum partition size of 2TB, with 4 primary partitions or 3 primary partitions and 1 extended partition. To create more than 4 partitions on an MBR disk, you should create (up to) 3 primary partitions and then 1 extended partition so that you can create multiple sub-partitions (logical drives).
▶GPT is the abbreviation of GUID Partition Table. It has no restrictions on partition numbers and disk sizes. GPT system disks can only be booted from UEFI (Unified Extensible Firmware Interface) enabled systems. Only users whose computer motherboards support UEFI can use GPT to create an unlimited number of partitions and take advantage of larger hard drives. However, the GPT structure cannot be used for removable media (USB sticks, CDs, DVDs, etc.).
Why migrate MBR OS to GPT disk?
As you can see, MBR and GPT are two different disk partition styles. But GPT is better than MBR format. It can support 2 TB+ hard drives and contain up to 128 primary partitions.
Besides, GPT disks use UEFI boot mode, which is more advanced than Legacy BIOS for MBR disks. Because UEFI can directly start the operating system after initialization, skip the BIOS self-check process, and finally achieve faster startup. Many users want to migrate MBR OS to GPT disk to enjoy more efficient disk space and faster boot speed.
In addition, if you want to upgrade Windows 10 to Windows 11, you have to convert system disk from MBR to GPT or clone MBR disk to GPT disk. Because Windows 11 can only boot from UEFI boot mode.
Powerful tool: migrate MBR OS to GPT disk without boot failure
To migrate OS from MBR disk to GPT SSD or HDD successfully, the safest and easiest way is to choose a powerful MBR to GPT migration tool. Here we would like to recommend the AOMEI Partition Assistant Professional (suitable for Windows 11/10/8/7/Vista/XP users). Its “Migrate OS to SSD” can migrate OS from one disk to GPT/MBR disk while Windows running. And after migration, not only the target disk can be booted, but no data is lost.
In fact, AOMEI Partition Assistant Professional is far more than a migration tool. It is an all-in-one partition disk manager, there are more advanced features you can try. Please download the demo version to see how to migrate MBR OS to GPT disk.
Now, I will demonstrate how to migrate MBR OS from MBR to GPT disk with AOMEI Partition Assistant Professional for you.
Step 1. Preparation
1. Connect or install a second SSD directly to your desktop or laptop. If your device has only one disk slot, you may need a SATA to USB adapter and cable to connect it.
2. Please check whether your motherboard supports UEFI boot mode and make sure it can be enabled in the BIOS. Otherwise, your PC will not start up normally.
3. Make sure the destination GPT SSD has large enough unallocated space or at least equal size to the original system partition on the source MBR disk. Otherwise, you can shrink or delete other partitions to get enough unallocated space, or shrink the original boot partition to make it easier to fit on the target SSD drive.
Step 2. Begin OS migration
1. Run AOMEI Partition Assistant Professional and you can see all the partitions and disks available. Then select the option “Migrate OS” from the "Clone" feature in the top toolbar.
2. In the next pop-up window, select the unallocated space on the GPT disk as destination location.
3. In the next screen, you can adjust the partition size on the disk if needed and then click “Next”. You can also resize system partition after the migration without data loss.
4. Here comes a note on how to boot from the destination disk. Read it and click on “Finish”.
5. Preview the partition layout and click "Apply" to apply all operations if no problem.
Step 3. Boot from GPT disk
After cloning the MBR OS to GPT disk, you need to change the boot mode from Legacy to UEFI as MBR and GPT have different boot modes:
1. After the computer restarts, long press "F2" or other keys such as DEL to enter the BIOS environment.
2. Change the boot order and set the GPT disk as the first boot device in the BIOS.
3. Change the boot mode from Legacy to UEFI.
4. Then save the changes, and you will successfully boot the OS from the GPT disk.
This is the whole process to migrate MBR OS to GPT disk and boot from it without any issues. If you have any partition-related issues, or you want to experience Windows 11, then this partition magic will definitely be your perfect assistant. By the way, Windows Server users need to upgrade to AOMEI Partition Assistant Server.