MBR2GPT — Convert MBR Disk to GPT Without Data Loss
Official Windows tool to convert the system disk partition scheme from MBR to GPT without erasing data. Required to enable UEFI / Secure Boot. The conversion is irreversible.
SystemWindows 10 / 11 (64-bit)
EnvironmentWinPE or Windows + /allowFullOS
PrivilegesAdministrator
First step — Verify the disk is MBR
PowerShell — "Partition Style" column shows MBR or GPT
DiskPart / WinPE — Gpt column blank = MBR · asterisk (*) = GPT
Specific disk — replace 0 with your disk number
Get-Disk | ft -Auto
diskpart
list disk
Case 1 — Validate only (no changes made)
System disk (general use, no need to specify disk number)
mbr2gpt.exe /validate
mbr2gpt.exe /validate /disk:0
Case 2 — Convert from WinPE (recommended)
Boot from WinPE or Windows Recovery USB, open CMD
mbr2gpt.exe /convert /disk:0
Case 3 — Convert from running Windows
CMD as Administrator — creates EFI partition by shrinking the OS partition
mbr2gpt.exe /convert /disk:0 /allowFullOS
Case 4 — Secondary disk with saved logs
Change /disk:1 to your target disk number
mbr2gpt.exe /convert /disk:1 /logs:C:\MBR2GPT_Logs /allowFullOS
Required post-conversion step
Enter firmware (BIOS) and change boot mode from Legacy / CSM → UEFI. Without this step the machine will not boot after conversion.
IRREVERSIBLE — Back up data first
Microsoft Docs