Convert MBR to GPT Without Losing Data

Updated on: December 18, 2019

This article introduces how to convert MBR to GPT disk on Windows 10/8/7 and Windows Server 2019/2016/2012/2008/2003 R2, change mbr disk to gpt without losing data.

Nowadays, hard disk size becomes larger and larger, it is common to use 2TB to 4TB HDD for personal computers. To use 2TB+ space, you must use GPT style disk. Besides capacity usage, GPT disk has many other advantages, so many people want to convert disk from MBR to GPT without losing data.

Windows built-in Disk Management utility can help you convert disk between MBR and GPT, but you have to delete all partitions in the disk first. To convert MBR disk to GPT without deleting partitions or losing any data, you need to run mbr2gpt.exe command tool or 3rd-party software. This article introduces detailed steps to convert MBR to GPT with both tools.

How to identify if the disk is MBR or GPT?

There are two ways to identify the disk type by native Disk Management and 3rd party software. Every disk is marked as MBR or GPT by NIUBI Partition Editor, after starting it, you'll see disk type immediately and clearly.

In Disk Management:

1. Right click this disk and select Properties:

Disk Management

2. Switch to Volume tab in the pop-up window.

GUID disk

How to convert mbr disk to gpt without Operating System

To data only disk, it is extremely easy to convert MBR to GPT via several clicks.

Applies to: Windows 10, Windows 8, Windows 7, Windows Server 2019, Windows Server 2016, Windows Server 2012 (R2), Windows Server 2008 (R2), Windows Server 2003 (R2).

  1. Download NIUBI Partition Editor, right click the front of the MBR disk and select "Convert to GPT Disk".
  2. Simply click Yes to in the pop-up window to confirm, then a pending operation will be added.
  3. Click Apply on top left to execute, done. (All operations before clicking Apply only work in virtual mode.)

Watch the video how to convert MBR disk to GPT without losing data:

Video guide

How to convert system mbr disk to gpt without data loss

There are some 3rd-party software that can convert MBR to GPT for system disk, but few can ensure 100% system bootable. If you want to convert a MBR system disk to GPT, it is suggested to run MBR2GPT which is provided by Microsoft.

MBR2GPT.exe is running from command prompt. On Windows Server 2019 and Windows 10 (1703 and subsequent versions), you can convert MBR to GPT with this command in Windows. For other Operating System, you need bootable media with Windows Preinstallation Environment (Windows PE).

To convert with MBR2GPT command, your disk partition should meet for the requirements, otherwise, the conversion can't be successful.

  1. The disk is currently using MBR
  2. There is enough space not occupied by partitions to store the primary and secondary GPTs: 16KB + 2 sectors at the front of the disk and 16KB + 1 sector at the end of the disk.
  3. There are maximum 3 primary partitions in the MBR partition table
  4. One of the partitions is set as active and is the system partition
  5. The disk does not have any extended/logical partition
  6. The BCD store on the system partition contains a default OS entry pointing to an OS partition
  7. The volume IDs can be retrieved for each volume which has a drive letter assigned
  8. All partitions on this MBR disk are recognized by Windows.

In general, you just need to pay attention to number 3, 5 and 8. If there are more than 3 partitions, or even one Logical partition, or any non-support partition such as EXT2/3 in the disk, MBR2GPT.exe can't convert MBR disk to GPT.

Common issue and corresponding solution

"Validating layout, disk sector size is: 512 bytes Disk layout validating failed for disk 0", "MBR2GPT: Conversion failed". This is the most common error message while converting MBR disk to GPT. If you received such error, check your disk partition configuration again.

In most of system disk, there are System Reserved, C: (for OS) and D drive. If all these partitions are Primary, you can convert this disk successfully.

Partition layout

How to convert system MBR disk to GPT in Windows

Applies to: Windows 10 (1703 and subsequent versions), Windows Server 2019

If you do not know your Windows 10 version, press Windows and R together on the keyboard, type winver and press Enter.


As you see, my Windows 10 is version 1903, so my system MBR disk can be converted in Windows without other tools.

If you want to convert MBR to GPT for system disk in Windows 10 1703 previous versions or Windows Server 2016/2012/2008, you need Windows Preinstallation Environment, because MBR2GPT.exe is not integrated in these versions. In that case, jump to next section.

If you are running the supported versions, it is very easy to convert MBR system disk to GPT. However, there's an issue you should pay attention to.

Disk partition structure before converting MBR to GPT:

Before converting

Disk partition structure after converting MBR to GPT:

After converting

As you see in the screenshot, after converting to GPT disk, original C drive was shrunk and a 100MB EFI system partition was created. This EFI partition can't be resized or moved in Disk Management or by other software. It means that C: drive cannot be extended in the future. There are 2 solutions:

Steps to convert MBR to GPT for system disk in Windows 10 and Windows Server 2019:

  1. Click Windows flag on bottom left, type cmd, select Run as Administrator.
  2. In command prompt window, type MBR2GPT /convert /allowFullOS and press Enter.

Note: this conversion can't be undone, so before doing this, make sure your computer can boot from UEFI.


How to convert MBR to GPT with MBR2GPT from bootable media

Applies to: Windows 10, Windows 8, Windows 7, Windows Server 2019, Windows Server 2016, Windows Server 2012 (R2), Windows Server 2008 (R2).

  1. If your System Reserved partition is 500MB or smaller, follow the steps to expand it larger (it's enough to add 500MB), otherwise, MBR2GPT will shrink C drive and create EFI partition behind it. If your System Reserved partition is larger than 500MB, do NOT expand it, just ignore this step.
  2. If you use Windows 10/8/7, download MediaCreationTool from here, if you use Windows Server 2019/2016/2012/2008, download Windows Server 2019 ISO from here. Then create bootable DVD disc or USB flash drive with Windows built-in or third-party tool.
  3. Boot from this bootable media, simply click Next in first Windows Setup window, then click Repair your computer on bottom left corner of next window.

    Setup window

    Repair computer

  4. Click Troubleshoot in next window, then click Command Prompt.


    Command Prompt

  5. In the command prompt window, type MBR2GPT /convert and press Enter.

In Summary

It is very easy and fast to convert MBR data disk to GPT for all Windows versions. If you want to convert MBR system disk to GPT, it requires much more steps with MBR2GPT command tool. Firstly, you should move or convert partition to meet the conditions of MBR2GPT. Secondly, check your Windows version, if it is Windows 10 1703 subsequent version or Server 2019, you can convert MBR to GPT in Windows. To other versions, you need to run MBR2GPT from bootable media.