Source: Windows Central

If you plan to upgrade Windows 10 to Windows 11, or want to switch the firmware type from the Basic Input/Output System (BIOS) to Unified Extensible Firmware Interface (UEFI) without modifying the current installation or deleting the data stored on the drive, you first need to convert the drive using a Master Boot Record (MBR) to a GUID Partition Table (GPT) partition style using the MBR2GPT command-line tool.

BIOS is an essential piece of code that resides on a special chip on the motherboard that enables the connection between hardware and software. This code has been around for a long time, and while it worked well, it was never designed for modern hardware, and it had many limitations, including limitations to partitions smaller than 2TB.

UEFI is the new firmware that replaces the old BIOS firmware style. It introduces several additional features, including support for partitions larger than 2TB and faster startup, sleep, resume, and shutdown times. Also, it unlocks many of the new security features available on Windows 11 and Windows 10. For example, "Secure Boot" is a feature that can protect a device's startup process from malicious programs, and now it's a prerequisite to install Windows 11. "Device Guard" gives you more advanced controls for app access, and "Credential Guard" can help prevent pass-the-hash attacks.

In this Windows 10 guide, we will walk you through the steps and information you need to know to use the Microsoft MBR2GPT command-line tool to convert a drive from MBR to GPT partition style, to switch from BIOS to UEFI mode on your device, and enable Secure Boot correctly.

Warning: Although this is a non-destructive process, it's still recommended to make a full backup of your PC before proceeding in the case that something goes wrong and you need to roll back.

How to convert a drive from MBR to GPT on Windows 10

Unlike previous methods requiring you to back up your data and reinstall Windows, the MBR2GPT tool streamlines the process to change partition styles in minutes. The conversion is done by adding the GPT components to the MBR partition without modifying the existing partition and keeping the data untouched.

Typically, you want to start in UEFI mode from the moment you first install Windows 11. However, if you upgrade a device running Windows 10 or an older version and supports UEFI, you can convert the drive to change the system firmware settings properly. Otherwise, the device will no longer start correctly.

Check MBR or GPT partition style

Before modifying the system configuration, you want to check the current settings to see whether the system is set to MBR or GPT using these steps:

  1. Open Start.
  2. Search for Disk Management and click the top result to open the experience.
  3. Right-click the drive (where Windows 10 is installed) and select the Properties option.

    Source: Windows Central

  4. Click on the Volumes tab.
  5. Under the "Partition style" field, if the field reads GUID Partition Table (GPT), the drive does not need conversion, but if you see the Master Boot Record (MBR) label, you can use the conversion tool to switch.

    Source: Windows Central

  6. Click the Cancel button.

Once you complete the steps, you can proceed to change the partition style on the computer.

Also, if you need to change the partition, make sure to check your device manufacturer's support website to find out whether the hardware includes support for UEFI before using these instructions.

Convert MBR to GPT partition style (offline)

To convert a drive using MBR to GPT on Windows 10, use these steps:

  1. Open Settings.
  2. Click on Update & Security.
  3. Click on Recovery.
  4. Under the "Advanced startup" section, click the Restart now button.

    Source: Windows Central

  5. Click the Troubleshoot option.

    Source: Windows Central

  6. Click on Advanced options.

    Source: Windows Central

  7. Click the Command Prompt option.

    Source: Windows Central

  8. Select your administrator account and sign in (if applicable).
  9. Type the following command to validate that the drive meets the requirements and press Enter:

    mbr2gpt /validate

    Source: Windows Central

    Quick tip: The mbr2gpt.exe is located in the "System32" folder inside the "Windows" folder. If you want to see all the available options, use the mbr2gpt /? command.

  10. Type the following command to convert the drive from MBR to GPT and press Enter:

    mbr2gpt /convert

    Source: Windows Central

  11. Click the Close button.
  12. Click the Turn off your PC option.

After you complete the steps, several actions will take place, including validating the drive and creating an EFI system partition (ESP). The UEFI boot files and GPT components will be added to the partition. The MBR2GPT tool will update the Boot Configuration Data (BCD), and the previous letter will be added to the drive.

Convert MBR to GPT partition style (online)

Whenever possible, it's recommended to use the MBR2GPT tool when Windows is offline to avoid potential problems. However, you can also use it when Windows 10 is fully functional.

To convert a drive from MBR to GPT, use these steps:

  1. Open Start.
  2. Search for Command Prompt, right-click the top result, and select the Run as administrator option.
  3. Type the following command to validate the drive and press Enter:

    mbr2gpt /validate /allowFullOS

    Source: Windows Central

  4. Type the following command to convert the drive to GPT and press Enter:

    mbr2gpt /convert /allowFullOS

    Source: Windows Central

Once you complete the steps, the command-line tool will shrink the primary partition and switch the drive from MBR to GPT.

MBR2GPT return codes

If the processes are completed successfully, the return code should be "0," but if the process fails, you may see one of the 11 error codes:

Return code Description
1 User canceled the conversion.
2 Internal error.
3 Initialization error.
4 Invalid command-line parameters.
5 Error on the geometry and layout of the selected disk.
6 One or more volumes on the disk are encrypted.
7 Geometry and layout of the disk don't meet requirements.
8 Error while creating the EFI system partition.
9 Error installing boot files.
10 Error while applying GPT layout.
100 Successful conversion, but some boot configuration data didn't restore.

MBR2GPT important details

The MBR2GPT tool works on a traditional hard drive (HDD), solid-state drive (SSD), and even an M.2 drive with any version of Windows 10, but you must run the tool from a computer running Windows 10, version 1703 or later.

The tool has been designed to convert drives running Windows 8.1, 7, or an older version, but you can upgrade the installation to the latest version of Windows 10 and then use the tool to convert from MBR to GPT.

When dealing with a drive using file encryption with BitLocker, you must first suspend the encryption before following the instructions outlined above.

Finally, while MBR-style drives can have up to four primary partitions, the drive you want to convert can't have more than three partitions because one additional allocation is required to create the UEFI partition.

How to change the firmware mode from BIOS to UEFI

Once you have converted the drive to a GPT partition style, the device will no longer boot until you access the motherboard's firmware and switch from BIOS to UEFI.

Usually, this process requires hitting one of the function keys (F1, F2, F3, F10, or F12), Esc, or Delete key as soon as you start the computer. The only caveat is that these settings will be different per manufacturer and even by computer model. As a result, make sure to check your device manufacturer's support website for more specific details.

While in the firmware interface, find the "Boot" menu, and enable the UEFI option, save the changes, and then the computer should start correctly.

Also, if you plan to upgrade the device to Windows 11, while in the UEFI settings, open the boot or security settings page, select the "Secure Boot" option and enable it, and exit the firmware saving the changes.

Check GPT partition style

To verify the computer is using a GPT partition style, use these steps:

  1. Open Start.
  2. Search for Disk Management and click the top result to open the experience.
  3. Right-click the main drive and select the Properties option.
  4. Click on the Volumes tab.
  5. Under the "Partition style" field, the information should now read GUID Partition Table (GPT).

    Source: Windows Central

After completing the steps, if the partition is running using the correct partition style, the last thing is to check whether the device is using the UEFI firmware mode.

Check UEFI firmware

To verify that your computer is using UEFI mode and Secure Boot is enabled, use these steps:

  1. Open Start.
  2. Search for msinfo32 and click the top result to open the System Information app.
  3. Click on System Summary on the left pane.
  4. Check the "BIOS Mode," which now should read UEFI.

    Source: Windows Central

  5. Check the "Secure Boot State" information, which now should read On.

Once you complete the steps, if the System Information shows UEFI, you have successfully switched the firmware modes.

More Windows resources

For more helpful articles, coverage, and answers to common questions about Windows 10 and Windows 11, visit the following resources: