By AOMEI / Last Updated September 11, 2019

Reasons to convert MBR to GPT

As you know, GPT and MBR are two different disk types. Nowadays, people are more likely to use GPT disk because of its prominent advantages. Compared with MBR disk, GPT disk can make use of a very large space that is more than 2TB limit of MBR disks. GPT disks allow an almost unlimited number of partitions. Each GPT partition has a unique identification GUID and a partition content type. And you can have more primary partitions.

General introduction to MBR2GPT

If your disk is MBR style and you want to convert it to GPT, you can use MBR2GPT. MBR2GPT is a Windows built-in tool which first introduced in Windows 10 version 1703 (also known as the Creator's Update). MBR2GPT.EXE converts a disk from the Master Boot Record (MBR) to the GUID Partition Table (GPT) partition style without modifying or deleting data on the disk. This tool is available in both the full OS environment and Windows PE.

Cannot create EFI system partition using MBR2GPT

Upon most occasions, MBR2GPT works well. However, sometime, you will receive error message conversion failed while creating the EFI system partition. It means you cannot create EFI system partition using MBR2GPT. Many things may cause this error.

1. This disk has more than 4 primary partition.

2. There are many bad sectors on the disk.

Therefore, you should try to delete MBR partition to reduce MBR partition to 3 and check bad sectors and repair disk.

Matters need attention when using MBR2GPT

1. Although, MBR2GPT is available in the full OS environment, it is much better to use it in WinPE, because it is more pure and more suitable for the conversion.

2. Before conversion, you should check if the version is 1703 or higher. You can Press Win + R and type winver to check the version.

3. Check if the disk is encrypted. If it is, unlock it.

4. You must leave enough room for EFI partition, or you will receive the error message: MBR2GPT cannot find room for the EFI system partition.

How to use MBR2GPT properly?

Step 1. Run CMD as Administrator.

Step 2. You can check if the disk meets the conversion requirement with this command:mbr2gpt / validate / disk:0.

Step 3. Type mbr2gpt / convert / allowfullos and press Enter. If you need to specify the disk, you can type mbr2gpt / convert / disk 0 / allowfullos.


After Converting MBR to GPT, you should go to BIOS and then convert Legacy to UEFI mode.

An easier way to convert MBR to GPT

If you cannot create EFI system partition using mbr2gpt, you can turn to a professional third party tool – AOMEI Partition Assistant Professional. It can help us to convert MBR to GPT quickly and easily, no matter it is a system disk or a data disk. The detailed steps are as follows.

Step 1. Install AOMEI Partition Assistant and open the software.

Step 2. Right click disk you need to convert and choose Convert to GPT Disk.

Convert 3tb Mbr Disk To Gpt

Step 3. Click OK to confirm you are going to convert MBR to GPT. At last, click Apply to save the operation.

Ok 3tb Disk

Apply 3tb

Tips: After the operation finishes, don’t forget to go to BIOS and change Legacy to UEFI.

With the help of AOMEI Partition Assistant, you can easily solve the issue: “cannot create EFI system partition using MBR2GPT”. After the conversion, if you decide you still want to use MBR disk, you can simply convert GPT to MBR.