How to Convert MBR to GPT on Windows 10

In this tutorial you'll convert your disk from MBR (Master Boot Record) to GPT (GUID Partition Table) on Windows 10 — without reinstalling or losing data — using Microsoft's built-in mbr2gpt tool. GPT supports larger disks, more partitions, and is required for UEFI boot (and for upgrading to Windows 11).

Step 1: Open Command Prompt as Administrator

1. Press the Windows key to open the Start menu.
2. Type cmd to search for the Command Prompt.
3. Right-click Command Prompt and select "Run as administrator".

Step 2: Validate the Conversion

In the Command Prompt, type the following command and press Enter:

mbr2gpt /validate /allowFullOS

This performs a validation to check if your system can be converted without issues.

Step 3: Convert MBR to GPT

1. If validation succeeded, run the conversion:

mbr2gpt /convert /allowFullOS

2. Once the conversion completes, close the Command Prompt and restart your computer.

Step 4: Access BIOS/UEFI Settings

During startup, press the key for your BIOS/UEFI settings. The key varies by make and model (commonly F2, F10, or Del).

Step 5: Change Boot Mode

1. In the BIOS/UEFI settings, locate the boot mode options.
2. Change the boot mode from Legacy/BIOS to UEFI (disable CSM if present).
3. Save the settings and exit.

Conclusion

Your system now boots using GPT and UEFI. You can verify in Disk Management (right-click the disk → Properties → Volumes → Partition style shows "GUID Partition Table"). This also unlocks Secure Boot, which Windows 11 requires.