How to Convert MBR to GPT without Deleting Partitions in Windows PC?

Basic knowledge of MBR and GPT

MBR (Master Boot Record) and GPT (GUID Partition Table) are two different types of partition structures. When you insert a new disk to your computer, you will be required to initialize it to MBR or GPT before you can save any data onto it. Meanwhile, the MBR is a default selection. So, what’s the major differences between MBR and GPT?

1. Max primary partition number

MBR only supports up to 4 primary partitions at most because it contains a 64-bit bytes partition table and each one will require 16 bytes. If you need more than 4 primary partitions, you have to convert the fourth primary partition to an extended partition, within which you will be able to create around 128 logical drives (also called sub-partitions). By contrast, GPT supports up to 128 primary partitions since it contains 16,384 bytes partition table and each one needs 128 bytes.

1. Max disk size

MBR only supports up to 2TB hard disk at most. That is to say, if a hard disk is larger than 2TB, the remaining size will show as “Unallocated” in Disk Management and not be usable. In GPT, each partition can hold up to 2^64 blocks in length, which is equivalent to 9.4 ZB. However, in practice, the maximum size on Microsoft Windows OS is limited to 256TB.

1. Operating system support

MBR, using Legacy BIOS boot mode, is more compatible with newer or older Windows operating system. However, GPT disk, using UEFI boot mode, can only be used as the boot disk when it is the 64-bit editions of newer OS like Windows 7 or Windows Server 2003 and their later versions  that support UEFI or EFI boot mode.

How to convert MBR to GPT without losing data?

From above, it is easy to get that GPT is relatively more superior than MBR. Therefore, you might want to convert MBR to GPT. To finish this, Disk Management is a nice choice. But it requires you to delete all existing partitions before conversion. Of course, that will lead to data loss. 

After you delete partitions on the target MBR disk, the option “Convert to GPT Disk” will become clickable. Otherwise, it will be greyed out.

To avoid that, you can either first back up important data, or turn to a free partition manager (AOMEI Partition Assistant Standard), which allows you to directly convert MBR to GPT or GPT to MBR without removing partitions (limited to data disk). You can download the freeware on AOMEI official site and take the steps to change MBR partition style to GPT without data loss.

PS.: this software can work well under all editions of Windows 10/8/7 and Windows XP/Vista, no matter it is 32-bit or 64-bit.

Step 1. Install and launch AOMEI Partition Assistant Standard. Right click the MBR disk and choose “Convert to GPT Disk”.

Step 2. Click “OK” to confirm the operation if everything is correct.

Step 3. Click “Apply” to commit the pending operation.

Wait for it to be done, and then you will find the MBR has been converted to GPT partition style successfully.

Additional fantastic features of free AOMEI Partition Assistant

Apart from allowing users to free convert MBR to GPT/GPT to MBR, the AOMEI Partition Assistant Standard also comes with many other amazing functions to make it as easy as pie to manage disk partitions on Windows PC. They mainly include:

• Resize (shrink or extend) partition in a flexible way;
• Move partition and merge partitions;
• Copy partition to another drive or disk;
• Convert file systems between FAT32 and NTFS without formatting;
• Format partition to NTFS, FAT32, exFAT, Ext 4, Ext3 and Ext 2;
• Delete or wipe partition;
• Change drive letter and label;
• Check partition for bad sectors and fix them;
• Clone hard disk;
• Wipe hard disk and write zeros to each sector;
• Make bootable media to repair Windows boot issues
• Transfer OS from MBR disk to MBR disk;
• More….