By AOMEI / Last Updated August 19, 2019

Convert to GPT Disk Grayed Out in Windows Disk Management

As we all know, the maximal size of MBR disk is limited to 2TB and only supports four primary partitions. However, GPT sustains 128 primary partitions and more than 16 million TB. Therefore, in order to build more partitions or take full advantage of disk space, you need to convert MBR to GPT. Furthermore, compared with MBR, GPT has better compatibility. You can learn more differences between them in MBR & GPT.

Disk Management is a built-in partition tool of Windows that enables you to convert MBR to GPT disk. However, when you go to Disk Management and right click the MBR disk, you may find the option “Convert to GPT Disk” grayed out.

Convert to GPT

There are two factors account for Windows Convert to GPT greyed out. One is partition existing on the disk, and the other is the selected disk contains system files. Of course, if you really want to convert MBR to GPT with Disk Management, the only way is to back up all the data on disk 0 and then delete all partitions.

However, this is impossible actually because deleting all data includes uninstall the system. And Windows does not allows you to do this. To avoid data loss, you can backup disk first and perform the conversion. After that, restore all data. Obviously, it is a time-consuming and error-prone process. Two other better solutions for this disabled convert to GPT issue would be:

  • Convert to GPT via CMD (better for data disk that does not contain system)

  • Convert to GPT without losing data via AOMEI Partition Assistant Professional.

Steps to Convert to GPT without Data Loss

AOMEI Partition Assistant Professional is reliable and powerful partition manager that can help you convert MBR to GPT without losing any data, given that you can’t convert to GPT disk using Windows tool. Compared with Disk Management, this software is more freely for you because you can convert MBR to GPT directly. Besides this function, you can resize partition, move partition, merge partitions, make bootable CD, and so on. Windows 10, 8.1/8, 7, XP, Vista are supported.

Step 1. Install and launch AOMEI Partition Assistant. Right-click the disk you want to convert and select “Convert to GPT Disk”.

Convert Data Disk to GPT

Step 2. Click "OK" after confirming the operation.

OK to GPT Data Disk

Step 3. You can preview the conversion. To save the change, please click "Apply" on the toolbar.

Apply to GPT Data Disk

Tips: If you encounter convert to GPT unavailable in Server 2003, 2008 and 2012, please turn to AOMEI Partition Assistant Server edition.

Convert to GPT via Command Prompt

Step1. Click Start, type "cmd", and right click it, select "Run as Administrator", or press "WIN+R", type "cmd" and press Enter to open the command prompt. Then, input "diskpart" to run the utility.

Step2. Type "list volume" and make sure if there are any partitions or volumes on the MBR disk. If there are, you need to use diskpart delete partition first.

Then, type "list disk", and press Enter, it will show you all the disks on your computer. Make note of the disk number that you want to convert to GPT disk. Here take disk 1 as an example.

Step3. Type "select disk 1", press "Enter", it will remind you that the disk 1 is selected.

Step4. Type "convert gpt", press "Enter" to submit the operation. Wait a second, you will find the Command Prompt says DiskPart successfully converted the selected disk to GPT format. Please take a look at the following screenshot.

diskpart convert to gpt


Although most of the users choose to convert MBR to GPT, some of them need to convert GPT to MBR due to Windows 2000, Windows 2003 32-bit, or Windows XP 32-bit version does not support GPT partitions. A GPT disk will be showed as GPT protective partition in these systems, in this situation if you want to access data in these systems, you need to convert GPT to MBR. Fortunately, AOMEI Partition Assistant can also help you convert GPT to MBR.


  • For system boot disk conversion between MBR and GPT styles, to guarantee system bootable, you need to enter BIOS and change the boot mode after the conversion is completed. For more information on BIOS and EFI (UEFI), please refer to GPT formatted disk legacy boot not supported.

  • For conversion between MBR and GPT disks on Laptop, please make sure the power supply is sufficient.

  • To ensure the data is consistent, do not abnormally terminate the program during the conversion process.

  • When you are unable to convert disk to GPT on external hard drive or a secondary storage, the free tool, AOMEI Partition Assistant Standard, can help you convert between MBR and GPT on data disk without data loss.