What’s the Difference Between GPT and MBR When Initializing or Converting a Disk?

Set up a brand new HDD or SSD on Windows 8.x or 10 and you’ll likely be asked whether you want to use the MBR or GPT partition structures.

Many people have no idea of this issue so that they have to be hesitating when making a choice between MBR and GPT, and they eagerly hope someone could tell them which one is better or which one they should choose.

MBR vs. GPT: The Difference

MBR stands for Master Boot Record while GPT represents GUID Partition Table, and they are 2 partitioning schemes for HDD, SSD and removable devices.

To know what partitioning scheme your hard disk is employing, just download and install MiniTool Partition manager, which is a free partitioning software to help users explore disk/partition properties, initialize disk (to MBR or GPT), enlarge a partition, change partitioning scheme between MBR and GPT, convert file system between FAT32 and NTFS, and so on.

Then, launch the freeware to get the main window:

From the screenshot you can see I have 2 disks: one MBR and one GPT.

Since MBR and GPT are partitioning schemes, they are doing the same thing: manage how partitions are created and organized on a hard disk, but they differ from each other in many aspects.

Firstly, MBR and GPT Were Introduced in Different Time

MBR was introduced with IBM PC DOS 2.0 in March 1983 and it is used till now. However, GPT was developed in the late 1990s as part of what eventually became UEFI, and it becomes popular just in recent years.

Secondly, MBR and GPT Have Different Structures

MBR consists of 3 parts, including master boot code, a partition table for the disk, and disk signature. A partition table can hold maximum number of 4 entries for primary partitions in Windows.

However, a GUID Partition Table is composed of a Protective MBR which is used in a way that prevents MBR-based disk utilities from misrecognizing and possibly overwriting GPT disks, a primary GUID partition table header which records its own size and location and the size and location of the secondary GPT header, a primary GUID Partition Entry Array, a backup GUID Partition Entry Array, and a backup GUID Partition Table Header. A GUID partition table could contain up to 128 partition entries in Windows.

Thirdly, Supports on Disk Capacity and Partition Amounts Are Different

Support on Partition Amounts
Since an MBR partition table can hold 4 primary partition entries at most, we are only allowed to create the maximum number of 4 primary partitions on an MBR disk. If we want to create more partitions, we have to create an extended partition where lots of logical partitions could reside. However, a logical partition can’t be set active.

On the contrary, a GPT disk theoretically allows an almost unlimited number of partitions, but Windows implementation restricts it to 128 partitions. Each partition on GPT can function like a primary partition on MBR disk.

Support on Disk or Partition Capacity
We can only use 2TB or 16TB of a hard disk’s capacity no matter how large the disk is, if we initialize it to MBR. If the disk is using the traditional 512B sector, we can only use 2TB. If it is using 4Kn (4K native) sector, we can use 16TB.

However, a GPT disk can be up to 2^64 logical blocks in length, and logical blocks could be 512 bytes or 4K in size. Therefore, a GUID partition table disk can grow to a very large size compared with MBR partition table disks. Actually, there is no need to talk about disk or partition capacity limit of GPT since there will be no hard disk exceeding the limit in a very long time.

Fourthly, MBR Differs from GPT in Compatibility

All current Windows operating systems can use GPT partitioned disks for data, such as Windows 7, Windows 8, Windows 10, Windows Server 2008, Windows Server 2012, and Windows Server 2016, but only their 64 bit versions support booting from GPT disk when UEFI boot mode is supported and enabled.

In addition, the 32 bit version of Windows XP can only see the Protective MBR, and even the 64 bit version can use GPT disk for data only.

At Last, They Have Different Boot Mode

If motherboard of our computer supports Legacy boot only, we can only boot Windows from MBR disk. To install Windows on GPT disk under this mode, you’ll receive the error message “Windows cannot be installed to this disk. The selected disk is of the GPT partition style”.

Or Windows won’t start if it is already installed on GPT disk under Legacy boot mode.

However, if motherboard of our computer supports UEFI boot only, we can only start Windows from GPT disk. To install Windows on MBR disk, you’ll receive the error message “Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disk”.

Similarly, Windows will be unbootable if it is already installed on MBR disk in UEFI boot mode.

But luckily, current motherboards support both Legacy boot and UEFI boot, so you only need to enable the CSM (Compatibility Support Module) in BIOS when you want to boot Windows from both MBR disk and GPT disk, or enable UEFI when you want to boot from GPT disk, or enable Legacy BIOS while you plan to boot from MBR disk.

In addition, even if your motherboard supports one boot mode only, you can still find solutions from the article Windows Cannot Be Installed to a Disk? Here Are Solutions.

It’s easy to initialize a new hard disk to either MBR or GPT, which could be done in both Windows Disk Management and MiniTool Partition Wizard.

Check out how.

Now, most of you would know the difference between MBR and GPT. You may read more about which partitioning scheme is better, MBR or GPT?