3 Ways to Change a Disk from Master Boot Record into GUID Partition Table

Learn how to use diskpart command-line, built-in disk management, and partition software to change a Master Boot Record disk into GUID Partition Table disk.

April 13, 2016

3 Ways to Change a Disk from Master Boot Record into GUID Partition Table

A MBR disk, short for master boot record, uses the standard BIOS partition table. However, a GPT disk, short for GUID partition table, is a new layout introduced with unified extensible firmware interface (UEFI). Because of the different partition tables, the GPT disks have two major advantages:

  • GPT disks supports up to 256TB per single partition. However, MBR disks supports up to 2TB per single partition.
  • GPT disks supports up to 128 primary partitions. However, MBR disks supports up to 4 primary partitions, or 3 primary partitions and 1 extended partition, which can be subdivided up to 128 logical volumes.

Generally there are three ways to change a master boot record disk into a GUID partition table disk. The Windows built-in Disk Management tool and Diskpart command line enable you to realize the conversion between MBR and GPT as long as the disk you want to convert does not contain any partitions or volumes. In other words, it is a process of losing data. Before you convert a disk, please make sure to backup anything that you do not want to lose on another hard disk.

The most convenient and safe way to convert MBR disk to GPT disk (or convert GPT disk to MBR disk) is using a 3rd party partition manager like AOMEI Partition Assistant, which can convert a disk between MBR and GPT without data loss.

Before you do

  • Removable disks cannot be changed into a GPT disk.
  • Windows XP 32-bit cannot support GPT disks, and 64-bit can only use GPT disks for data.
  • Only 64-bit version of Vista and above on UEFI-based systems can boot from a GPT disk.

WAY 1: AOMEI Partition Assistant converts MBR disk to GPT without data loss

AOMEI Partition Assistant is all-on-one partition manager software and magic disk tool which is designed for you to maintain and optimize your computer. It enables you to convert a disk from MBR to GPT easily and safely.

Tips:

  • You must be an administrator to do this in Windows.
  • Before converting a disk, we suggest you close any programs that are running on or from that disk.
  • To ensure the data is consistent, do not abnormally terminate the program during the conversion process.

Step 1: Download the right version according to your system, install and launch it. Right-click the MBR disk (here is Disk 2) you want to convert to GPT and select "Convert to GPT Disk" in the drop-down menu.

Step 2: It will ask you "Are you sure to convert the selected disk from MBR to GPT disk?". Click "OK" to confirm the change.

Step 3: To save the conversion, please click "Apply", and then click "Proceed" to perform the operation.

After the conversion is completed, you can create more primary partitions on GPT disk or add unallocated space (if disk is larger than 2TB) to existing partitions with AOMEI Partition Assistant.

WAY 2: Convert a disk from MBR to GPT with built-in Disk Management

To open Disk Management console, please right-click "(My) Computer" and select "Manage" -> click "Disk Management". Windows built-in Disk Management tool allows you to convert a disk to GPT format as long as it is empty. If the disk contains any partitions or volumes, you will find "Convert to GPT Disk" option is greyed out. In such case, you need to delete all partitions first.

Note: The following guide will result in data loss, please backup your important files before you convert a disk.

Step 1: Right-click the partition(s) on the disk you want to convert and select "Delete Volume".

Step 2: After all the partitions or volumes are removed one by one, the disk will show as "Unallocated". Then, right-click the disk and select "Convert to GPT Disk". In an instant the disk has been converted from MBR to GPT.

Now you can re-create partitions and restore your backed up data to the GPT disk.

WAY 3: Change a MBR disk to GPT disk with Diskpart

Like built-in Disk Management, Diskpart only supports for changing a disk to GPT as long as it does not contain any partitions or volumes. So back up your data if you don't want to lose anything important.

Step 1: Click "Start Menu" -> input "diskpart" in the search box and press "Enter" -> Click "Yes" to launch command prompt.

Step 2: Input "list disk" and press "Enter" to dispaly all disks in your computer.

Step 3: Input "select disk n" and press "Enter" to give a focus on the disk. n is the number of the disk you want to convert, and here take "Disk 1" for example.

Step 4: Input "clean" and press "Enter" to delete all partitions or volumes on the selected disk.

Step 5: Input "convert gpt" and press "Enter" to complete the conversion from MBR to GPT format.