By Michael / Last Updated June 25, 2021

Why change Master Boot Record to GUID partition table?

An 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 a unified extensible firmware interface (UEFI). Because of the different partition tables, the GPT disks have two major advantages:

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

Before change your disk from MBR to GPT,  you should realize the following things:

▪ 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.

MBR VS GPT

How to: Convert a disk from MBR to GUID partition table [3 ways]

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 back up 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.

WAY 1: Change disk from MBR to GPT without data loss 

AOMEI Partition Assistant  Standard 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 data disk from MBR to GPT easily and safely in Windows 10, 8, 7. If the disk that you want to change contains operating system, you need to upgrade AOMEI Partition Assistant Standard to an advanced edition

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.

Download Freeware Win 10/8.1/8/7/XP
Secure Download

Step 1. Download,  nstall 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.

Change Master Boot Record to GUID Partition Table

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.

OK

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

Apply

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 a case, you need to delete all partitions first.

Convert to GPT Greyed Out

Note: The following guide will result in data loss, please back up 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".

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.

Convert to GPT

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

WAY 3: Change Master Boot Record to GUID partition table via Diskpart 

Like built-in Disk Management, Diskpart only supports 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 display all disks on 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.

Convert MBR to GUI partition table