How to Convert an MBR disk to GPT via Powershell?

July 10, 2018

This article shows you how to convert an MBR disk to GPT using Windows Powershell or AOMEI Partition Assistant in detail.

Why need to convert an MBR disk to GPT?

We may want to reinstall Windows operating system after long use of your computer or the computer the computer infected with virus in daily use. However, you may find out that the computer hard drive is MBR partition style and the operating system going to be installed needs a GPT disk with the error message – Windows cannot be installed on this disk. The selected disk has an MBR partition table. One EFI systems, Windows can only installed on GPT disks. Or you are not satisfied with the capacity of the existing disk and purchase a disk with larger capacity (beyond 2TB) but find that MBR disk doesn’t support more than 2TB; thus you need to change the partition style of disk from MBR to GPT.

About MBR and GPT

Before realizing how to convert a disk into GPT, have a basic understanding of MBR and GPT.

1. MBR and GPT disk are two different types of disk, the main difference lies in the partition structure and partitioning method. GPT disk is a new type of disk appeared in recent years.

GPT has more advantages than the Master Boot Record (MBR) partitioning method because it allows up to 128 partitions per disk, supports volume sizes up to 18 gigabytes, and allows partitioning of primary disks. And the backup disk partition table is used for redundancy and also supports a unique disk and partition ID (GUID).

2. GPT (Globally Unique Identifier Partition Table Format) is a kind of disk partitioning structure used by Extensible Firmware Interface (EFI) based on Itanium computer. Compared with Master Boot Record (MBR), GPT owns more advantages as it allows one disk to own partitions up to 128; supports volume size up to 18 gigabytes; allows the primary and secondary disk partition tables to be used for redundancy; supports unique disk and partition ID (GUID).

3. The features of MBR: supports up to 2TB and up to 4 primary partitions (or 3 primary partitions and 1 extended partition & unlimited logical partitions) on one disk.

4. The features of GPT: supports up to 18EB and 128 partitions on one disk. Unlike MBR partitioned disk, the critical platform operational data of GPT disk is located in partitions rather than hidden sectors. In addition, GPT disk has redundant primary and backup partition tables to improve the integrity of partition structure.

On current trends, GPT disk will gradually replace with MBR disk. Old machine may only support MBR disk while most newly purchased machine supports GPT disk.

Convert disk from MBR to GPT via Powershell

After realizing the features of MBR and GPT disk, it is time to learn how to using Powershell convert disk from MBR to GPT.

Method 1. During the normal use of computer, you can turn to Windows Powershell (command-line utility - CMD) to convert partition style to GPT by following the steps below:

1. Access CMD interface: Press Windows + R simultaneously, input “cmd” and hit Enter.

2. Input “diskpart” and hit Enter key.

Run Diskpart

3. Input “list disk” and press Enter key to list all disks connected to your machine. (Take converting disk 1 in the following screenshot to GPT as an example)

List Disk

4. As what you want to convert is disk 1, run “select disk 1” command and the interface will show that Disk 1 is now the select disk. And our all next operations will be for disk 1.

Select Disk

5. After choosing the target disk, what we should do is convert: Enter “convert gpt” and hit Enter key. Then the interface displays that Diskpart successfully converted the selected disk to GPT format.

Convert GPT

Methods 2: If you need to convert MBR to GPT in the Windows installation interface, press Shift + F10 to open CMD as administrator and do as the following steps (Note: this way will erase all data on the target disk, you’d better backup the disk in advance)

After accessing CMD interface, type the following command orderly and hit Enter after each command.

  • diskpart(to run Diskpart utility)

  • disks connected to the computer)

  • select disk 0(disk 0 is selected)

  • clean(remove all partitions on the disk)

  • convert gpt

  • list partition

  • create partition efi size=100( the default unit is M)

  • create partition msr size =128

  • create partition primary size =102400(the capacity of C drive that you want to create)

  • exit

After converting disk to GPT, you can enter the Windows installation interface to install Windows operating system.

Windows Powershell alternative to convert MBR to GPT

For some users, it might be a little difficult to using Diskpart to convert disk from MBR to GPT. Thus, you can turn to third party GUI software – AOMEI partition Assistant, which can not only convert MBR disk to GPT, but also convert GPT to MBR without data loss. See how it works.

PS.: Usually, converting MBR to GPT using AOMEI Partition Assistant will not make data loss on the target disk. But in order to avoid data loss caused by improper operations, you can back up the whole disk or important files on the disk using AOMEI Bakcupper.

Step 1. Right click the disk that you need to convert (here is system disk) and choose “Convert to GPT Disk”.

Convert to GPT Disk

Step 2. Click “OK” in the pop-up window. Then, click “Yes”.

Confirm Your Motherboard Support UEFI Boot

Step 3. You’ll back to the main interface, confirm your operation and click “Apply” > “Proceed” to perform it.

Notes:

  • You should ensure that your computer supports UEFI before converting system disk to GPT. And after converting, you need to change boot mode from Legacy to UEFI.

  • It is available to convert data disk from MBR to GPT disk via AOMEI partition Assistant as well.

Conclusion

You are certainly able to use Windows Powershell to convert MBR to GPT freely. But if you want to get an easier way to convert disk into GPT, AOMEI Partition Assistant will be a great choice, no matter for data disk or system disk. In fact, it is featured with more functions, such as migrate OS from MBR disk to GPT.