By Cherry / Last Updated March 17, 2022

What is a GPT disk?

GPT, short for GUID Partition Table, is a way to store the partitioning information on a hard drive. The information includes where partitions begin and end on the hard disk, so your OS is able to find out which sectors belong to each partition and which partition is bootable. This is why you should choose a partition table for your hard disk before creating partitions on it. A GPT disk supports up to 128 primary partitions and the maximum disk size allowed is at most 9.4ZB.  Meanwhile, if you try directly upgrading Windows 10 to Windows 11 with the “Check for update” feature, then, your boot disk must be in the GPT partition style and the boot mode of your motherboard must be UEFI.

What is an MBR disk?

MBR, short for Master Boot Record, was first introduced with IBM PC DOS 2.0 in 1983.  The reason why it’s called Master Boot Record is because the MBR is a special boot sector lying at the beginning of a drive. The sector has a boot loader for the installed OS and info about the drive’s logical partitions. The boot loader is a small bit of code that generally loads the larger boot loader from another partition on a drive. What’s more, if an MBR disk is a boot disk, to let Windows boot normally, the boot mode should be Legacy.

By comparison, GPT has more advantages over MBR although the latter one shares better compatibility with many old OSes.

1. A GPT disk supports at most 128 primary partitions while the number drops to 4 when it comes to an MBR disk.  In order to have more primary partitions on an MBR disk, you should convert one of the primary partitions to an extended partition and create logical partitions within it which is not a very good idea.

2. The maximum disk size of a GPT disk is 9.4ZB while it drops to only 2TB when it comes to an MBR disk. Thus, if you have a hard disk in MBR which is 3TB or 4TB large, only 2TB will be displayed as usable in File Explorer and when you run Disk Management to check it, you’ll find the extra space is marked as unallocated.

mbr vs gpt

The conversion between GPT disk and MBR disk

For different purposes, users sometimes need to make conversion between GPT disks and MBR disks. For example, when they find their 4TB drive only shows 2TB, then, converting MBR to GPT disk is a good idea; or sometimes, users may be prompted that “Windows cannot be installed to this disk. The selected disk is of the GPT partition style. The error suggests that the PC is set up to boot in Legacy while the boot disk is in GPT and they don’t match each other. In this case, you must convert GPT to MBR.

gpt error

When it comes to GPT MBR conversion, there’re several choices. Of course, the most notable ones are Windows built-in Disk Management utility and CMD DiskPart.

Here, I’ll use MBR to GPT conversion for example.

Use Disk Management

Disk Management, as mentioned above, is a Windows built-in tool. It’s able to manage hard disks and their partitions easily within only a few clicks. The operations it supports include partition deletion, partition formatting, and of course, MBR-GPT conversion.

1. Right-click on “This PC” on the desktop and select “Manage”.

2. Select “Disk Management” under the “Storage” tab.

3. Right-click on the target disk and select “Convert to GPT Disk” to start the conversion.

It seems pretty easy, right? However, when you reach step 3, you could find that the option “Convert to GPT Disk” is greyed out? How come? Actually, to run MBR-GPT conversion in Disk Management, you have to delete all existing partitions on the hard disk. If there’re partitions left, the option will be greyed out. In this case, users can suffer from severe data loss.

convert to gpt

Use DiskPart

Similar to Disk Management, DiskPart is another Windows built-in program developed to manage your hard disks and partitions. Users need to input corresponding command lines in DiskPart to execute different operations including partition extension, partition deletion, and GPT-MBR conversion.

1. Hit Windows key + R key at the same time and type “diskpart” in the box. Hit “ENTER”.

2. Type “list disk” and hit “ENTER” to list all existing hard disks on your PC.

3. Type “select disk n” to select the MBR disk you want to convert to GPT.

4. Type “clean” and hit “ENTER” to delete all partitions on the MBR disk.

5. Type “convert gpt” and hit “ENTER” to start the conversion process.

to gpt

Try the best third-party GPT-MBR converter without data loss

From the contents above, we can conclude that both Disk Management and DiskPart require partition deletion for MBR-GPT conversion. Since it causes severe data loss, is there any better alternative that is lossless? This time, I recommend AOMEI Partition Assistant Professional, a powerful and intuitive software utility that helps convert MBR to GPT or GPT to MBR without data loss. Moreover, many other features including primary to logical drive conversion and MBR to GPT OS migration are also available.

After seeing the general description of GPT and MBR disks, you may want to convert between the 2 partition styles. Download the demo of the most impressive disk manager to have a try!

Step 1. Install and launch AOMEI Partition Assistant Professional, right-click on the target disk and select “Convert to GPT Disk”.

convert t gpt

Step 2. When prompted with the message saying “Are you sure to convert the selected disk from MBR to GPT disk”, hit “OK” to proceed.

ok

Step 3. Hit “Apply” as the screenshot shows to commit the pending conversion operation.

apply

Conclusion

In this post, a general description of MBR and GPT disks are given and you now should have clearly understood what these 2 items are. Meanwhile, due to their different properties, users sometimes need to convert MBR to GPT or GPT to MBR. In this case, 3 practical ways for MBR-GPT conversion are given and among them, only AOMEI Partition Assistant Professional doesn’t cause any data loss. This software supports Windows 7/8/8.1/10/11/XP very well and if you’re a Server user, you should try the Server edition.