Forum Discussion
Safe way to convert mbr to gpt without formatting on windows 10?
I suggest using GPTGen as it is an open-source, command-line utility that rewrites the partition table only, turning a disk laid out with the legacy MBR scheme into a modern GPT in-place. Because it edits just a few sectors, the payload data on every partition stays intact—no copy-back or re-image step is required. The tool ships as a single EXE for Windows and also builds on Linux or macOS. You can use this free app to convert mbr to gpt on windows 10 in a safe way.
| Step | Command or action |
|---|---|
| 1. Download & extract | Grab the latest gptgen-1.2.1.zip from SourceForge, then unzip to C:\Tools\gptgen. |
| 2. Identify the disk | Open an elevated Command Prompt and run:diskpart → list disk → note the disk number you want (e.g. 0). |
| 3. Dry-run (optional but smart) | cd C:\Tools\gptgengptgen \\.\physicaldrive0This creates two image files (primary.img, secondary.img) instead of touching the disk, letting you confirm it will work. |
| 4. Commit the change | gptgen -w \\.\physicaldrive0The -w switch writes the new primary and backup GPT headers directly to the drive. The process is usually finished in seconds. |
| 5. Reboot & switch firmware | Enter BIOS/UEFI setup, change the boot mode to UEFI. |
| 6. (System disk only) rebuild boot files | Boot from a Windows 10/11 USB, open Command Prompt (Shift + F10) and run:diskpart → create a 100 MB FAT32 partition → assign letter Sbcdboot C:\Windows /s S: /f UEFI |
When to choose GPTGen for converting MBR to GPT
You’re comfortable with a CLI and want the lightest-touch conversion possible.
The disk is in a server or appliance where installing GUI partition software isn’t convenient.
You’re scripting a mass-deployment task and need a portable EXE that runs from WinPE.