How to Convert MBR to GPT Without Losing Data in Windows 11/10

Windows 11 requires a GPT disk with UEFI firmware to boot. If your PC still runs on an MBR disk with legacy BIOS, you need to convert the partition style before you can upgrade or use drives larger than 2TB.

This guide covers every method to convert MBR to GPT in Windows 10 and Windows 11, including the built-in MBR2GPT tool that keeps your data intact.

What Is the Difference Between MBR and GPT

MBR (Master Boot Record) is the legacy partitioning scheme tied to BIOS. It supports a maximum of 4 primary partitions and caps disk size at 2TB. GPT (GUID Partition Table) is the modern scheme tied to UEFI firmware. It supports up to 128 primary partitions and disk sizes up to 9.4 zettabytes.

If you plug in a large drive and see only part of its capacity, the disk is likely still formatted as MBR.

Before You Convert MBR to GPT

Back up your data first. Some methods erase all partitions on the disk, and even the non-destructive method carries risk if interrupted.

Check these points before you start:

• Confirm your motherboard supports UEFI boot mode. Systems running BIOS-only firmware cannot boot from a GPT system disk.
• Sign in with an administrator account. You must be a member of the Administrators group, or have equivalent privileges, to convert a disk.
• Close any programs that access the disk you plan to convert.
• Remove BitLocker encryption from the drive if it is enabled, since encrypted disks can block the conversion.

Method 1: Convert MBR to GPT Using MBR2GPT (No Data Loss)

MBR2GPT.exe is a built-in Windows tool available on Windows 10 version 1703 and later. It converts the system disk from MBR to GPT without deleting partitions or files. This is the safest method if you are upgrading your boot drive to UEFI.

Run MBR2GPT From Windows PE (Offline)

1. Select Start, click the Power icon, hold Shift, and select Restart to enter the Advanced Startup screen.
2. Go to Troubleshoot > Advanced options > Command Prompt.
3. Run the validation command first:

mbr2gpt /validate

4. If validation passes, run the conversion command:

mbr2gpt /convert

5. Restart the PC once the conversion finishes.

Run MBR2GPT From the Desktop (Online)

You can also run MBR2GPT from a live Windows 10 or Windows 11 session using the /allowFullOS switch, since the tool is normally restricted to the Windows Preinstallation Environment.

1. Open Command Prompt as administrator.
2. Run:

mbr2gpt /validate /allowFullOS

3. If the disk passes validation, run:

mbr2gpt /convert /allowFullOS

If validation fails with a message like “Disk layout validation failed,” the disk does not meet MBR2GPT’s structural requirements and you will need a different method or third-party tool.

Method 2: Convert MBR to GPT Using DiskPart (Data Loss)

DiskPart converts the partition style through Command Prompt, but it erases every partition on the disk first. Use this only on a disk with no data, or after a full backup.

1. Type CMD in the search box, right-click Command Prompt, and select Run as administrator.
2. Type diskpart and press Enter.
3. Type list disk and note the number of the disk you want to convert.
4. Type select disk X, replacing X with the correct disk number.
5. Type clean. This removes all partitions and files from the disk.
6. Type convert gpt.
7. Type exit to close DiskPart.

Method 3: Convert MBR to GPT Using PowerShell (Data Loss)

PowerShell offers a similar path to DiskPart with a few extra cmdlets.

1. Right-click the Windows icon on the taskbar and select Windows PowerShell (Admin).
2. Run Get-Disk to list all disks and identify the disk number.
3. Run Clear-Disk -Number X -RemoveData -Confirm:$false, replacing X with your disk number.
4. Run Initialize-Disk -Number X -PartitionStyle GPT.
5. Run Get-Disk again to confirm the partition style now shows GPT.

Method 4: Convert MBR to GPT Using Disk Management (Data Loss)

Disk Management gives you a graphical way to convert a disk, but like DiskPart, it requires deleting existing volumes first.

1. Select Start, type diskmgmt.msc, then select Enter.
2. Right-click each volume on the target disk and select Delete Volume, then confirm with Yes. Repeat this step for every volume on the disk.
3. Right-click the now unallocated disk and select Convert to GPT Disk.
4. To confirm the conversion, right-click the disk, select Properties, open the Volumes tab, and check the partition style.

Enable UEFI Boot Mode After Conversion

Converting the disk to GPT is not enough on its own. If this is your system disk, you also need to switch the firmware boot mode from Legacy to UEFI, or Windows will fail to boot.

1. Restart the PC and press F2, F8, F12, or Del to enter BIOS setup, depending on your motherboard.
2. Locate the Boot menu and set Boot Device Control or equivalent to UEFI Only.
3. Move the UEFI OS boot entry to the top of the Boot Priority List.
4. Save changes and exit. The PC should now boot from the GPT disk.

What Causes MBR to GPT Conversion Failure

• The disk still contains partitions when using MBR2GPT, which expects a supported layout with free space for the EFI system partition.
• BitLocker encryption is active on the target drive.
• The account running the command lacks administrator privileges.
• The motherboard firmware does not support UEFI, which blocks booting from a GPT system disk regardless of conversion success.

Frequently Asked Questions

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