By AOMEI / Last Updated February 25, 2020

To Know MBR and GPT disk

MBR (short for Master Boot Record), the most important data structure on the disk, is created when the disk is initialized. MBR size is 512 byte, and contains a small amount of executable code called the master boot code, the disk signature, and the partition table for the disk. MBR is the first sector of a partitioned disk, and is not located in a partition. It is located at a Main Boot Record area in front of the first partition. When a hard disk has been partitioned with the MBR Partition Table scheme, the master boot record contains the primary partition entries in its partition table.

GPT (short for GUID Partition Table), is a standard for the layout of the partition table on a physical hard disk. GPT was introduced as part of the Extensible Firmware Interface (EFI) initiative. It provides a more flexible mechanism for partitioning disks than the older Master Boot Record (MBR) partitioning scheme that has been common to PCs, it is also used on some BIOS systems because of the limitations of MBR partition tables, which restrict maximum disk partition's size to 2 TB. GPT disk can exceed the limitation of 2TB to allow a much larger volume than 2TB.

MBR vs GPT disk

MBR diskGPT disk
The max capacity of partition2TB18EB
The number of partitionUp to 3 primary partitions and 1 extended partitionUp to 128 primary partitions and no extended partition
Supported OSsWindows AllWindows XP 64 bit
Server 2003 SP1
Windows Vista
Server 2008
Windows 7
Windows boot from the diskYesNo
Partition TableNo duplicateTwo duplicates in the first and last

Limitation of MBR partitioning: MBR disks support only four partition table entries. If more partitions are needed, a secondary structure - an extended partition is necessary. Extended partition can be subdivided into one or more logical drives. Only one extended partition can be present on any given drive.

GUID Partition Table (GPT): GPT is a new disk-partitioning scheme that is used by the EFI in Itanium-based computers. GPT is supported by 64bit Windows, HP-UX 11i V2, Linux for Itanium, Open VMS for Itanium etc. GPT offers more advantages than MBR partitioning. GPT benefits are below:

  • Partitions size: Can be up to 18 Exabyte

  • Number of Partitions: 128 partitions per disk

  • Integrity: primary & backup partition tables for redundancy

  • Partition Format: Well defined and fully self identifying, uses version number and size fields for future expansion

All Windows operating systems can not boot from GPT disk. Typically, Windows Setup can not allow install Windows to GPT disk. Windows will tell you that "Windows cannot be installed to this disk, the selected disk is of the GPT partition style". However, you can create GPT disk as a data disk if your operating systems support read/write a GPT disk. You can convert GPT disk to MBR, or MBR disk to GPT in Windows system.

How to covert GPT disk to MBR disk without losing data?

As we known, Windows Disk Management snap-in has the ability to convert to MBR disk, but the disk must be empty. If the disk contains partitions, the conversion feature in the drop-down menu will be greyed out after right clicking on the GTP disk. To perform conversion, you must back up data and delete partitions.

Convert to MBR disk Greyed out

In such case, AOMEI Dynamic Disk Manager allows you to convert GPT disk to MBR directly and keep data safe.

Note: Because the MBR disk only supports up to 4 primary partitions. Therefore, please ensure your GPT disk has 4 partitions at most.

Step1: Launch AOMEI Dynamic Disk Manager and select the GPT disk you want to convert. Then, click "Convert to MBR Disk" in the left navigation.

Convert Disk from GPT to MBR

Step2: In the pop-up window, just click "OK".

Convert Disk from GPT to MBR
Step3: Click "Commit" in the toolbar to perform the operation. Or hit "View Pending Operations" to commit the changes.

Click Commit
After rebooting computer, you will find GPT disk has been converted to MBR disk successfully. It is very easy and safe to use AOMEI Dynamic Disk Manager to convert disk from GPT to MBR (it supports both Windows 7/8/Vista/XP and Server 2003/2008/2011/2012). You can free download demo version and have a try.