Converting Your Hard Drive From MBR to GPT

What MBR and GPT are, and why you might need to switch

MBR (Master Boot Record) and GPT (GUID Partition Table) are two different ways your computer organizes the space on your hard drive. MBR is the older standard, limited to drives under 2 TB and a maximum of four primary partitions. GPT is newer and handles much larger drives with more partitions, and it's required if you're using a modern motherboard with UEFI firmware.

You might need to convert from MBR to GPT if you're upgrading to a larger drive, installing a newer operating system that requires GPT, or switching to a motherboard that only supports UEFI boot. The conversion itself erases everything on the drive, so this is not something you do casually — you'll need to back up all your files first.

The actual conversion takes about 10 to 30 minutes depending on your drive size and which tool you use. The process is straightforward, but the stakes are high because a mistake can leave your drive unreadable. This guide walks you through the safest method using built-in Windows tools.

Key Takeaways

Converting MBR to GPT erases everything on the drive, so back up all your files to an external drive or cloud storage before you start.
Windows includes a free tool called Diskpart that can do the conversion, but you need to open it as administrator and run specific commands in the exact order shown.
If your drive contains your Windows installation, you cannot convert it while Windows is running — you must boot from a Windows installation media or recovery environment.
After conversion, your motherboard must support UEFI firmware and be set to UEFI mode in the BIOS, or your computer will not boot from the converted drive.
If the conversion fails or you're unsure about any step, stop and consult your motherboard manual or contact the drive manufacturer's support.

Back up everything on the drive before you start

This step is non-negotiable. Converting MBR to GPT wipes the drive completely. Copy every file you need to an external USB drive, an external hard drive, or a cloud storage service like OneDrive or Google Drive. If the drive holds your Windows installation, you'll also need a Windows installation media (a USB drive with Windows on it) to reinstall afterward.

If you're converting a secondary drive that doesn't hold Windows, you can do the conversion while Windows is running. If you're converting the drive Windows is installed on, you'll need to boot from installation media first. Check your motherboard manual to see how to access the boot menu — usually it's a key like F12, F2, or Del that you press immediately when the computer starts.

Open Diskpart and identify your drive

Diskpart is a command-line tool built into Windows that can convert partition tables. Right-click the Start menu, select "Windows Terminal (Admin)" or "Command Prompt (Admin)" — the exact name depends on your Windows version. If you see a User Account Control prompt asking for permission, click Yes.

Type diskpart and press Enter. You'll see a new prompt that says DISKPART>. Now type list disk and press Enter. You'll see a list of all the drives connected to your computer, each with a number like Disk 0, Disk 1, and so on. Find the drive you want to convert by looking at its size — it should match the capacity of the physical drive you're working with.

Write down the disk number. This is critical: if you select the wrong disk, you will erase the wrong drive. Double-check the size against your drive's specifications before moving forward.

Select the disk and convert it to GPT

Type select disk X, replacing X with the number of your drive. For example, if your drive is Disk 2, type select disk 2 and press Enter. Diskpart will confirm with a message like "Disk 2 is now the selected disk."

Now type clean and press Enter. This command erases all data on the selected disk. Diskpart will confirm that the disk has been cleaned. Then type convert gpt and press Enter. The conversion usually completes in seconds, and you'll see a message confirming the disk is now GPT.

Type exit and press Enter to close Diskpart. Your drive is now formatted as GPT, but it has no partitions yet — it's blank. If this is a secondary drive you plan to use for storage, you'll need to create a new partition and format it. If this is your boot drive, you'll need to reinstall Windows.

Create a new partition if this is a secondary drive

If you converted a secondary drive (one that doesn't hold Windows), you need to create a partition on it before you can store files. Right-click the Start menu and open "Disk Management." You should see your newly converted GPT drive listed as unallocated space.

Right-click the unallocated space and select "New Simple Volume." A wizard will open. Click Next, set the size to the maximum (which uses the entire drive), click Next again, assign it a drive letter, click Next, and then choose a file system — NTFS is the standard for Windows. Click Next, check the "Perform a quick format" box, and click Finish. The drive will format in a few seconds and appear as a usable drive in File Explorer.

Reinstall Windows if you converted your boot drive

If you converted the drive that Windows was installed on, you now have a blank GPT drive with no operating system. You'll need to reinstall Windows. Insert your Windows installation media (a USB drive with Windows on it) and restart your computer. During startup, press the key that opens the boot menu — usually F12, F2, or Del, depending on your motherboard.

Select the USB drive from the boot menu. Windows Setup will start. Follow the on-screen prompts, and when you reach the screen asking where to install Windows, select the GPT drive you just converted. Windows will create the necessary partitions automatically and install. This process takes 15 to 30 minutes depending on your drive speed.

After Windows finishes installing, restart your computer and check that it boots normally. If it does not boot, restart and enter the BIOS (usually by pressing F2 or Del during startup). Look for a setting called "Boot Mode" or "UEFI/Legacy Boot" and make sure it's set to UEFI, not Legacy. Save and exit, and try booting again.

Verify the conversion was successful

Open Disk Management again (right-click Start, search for "Disk Management"). Find your converted drive in the list. If it shows as GPT, the conversion worked. You can also open Diskpart again, type list disk, and look at the GPT column — an asterisk (*) next to your drive number means it's now GPT.

If the drive still shows as MBR, or if you see an error message during conversion, the process did not complete. This usually means the drive had a partition or file that couldn't be erased. Restart your computer and try again, making sure you ran Diskpart as administrator and typed each command exactly as shown.

Frequently Asked Questions

Can I convert MBR to GPT without erasing the drive?

No. The conversion process requires a complete wipe. If you need to keep the files on the drive, copy them to external storage first, convert the drive, and then copy them back after the conversion is complete.

What if my computer won't boot after I convert the drive?

Your motherboard is probably still set to Legacy boot mode instead of UEFI. Restart the computer and enter the BIOS by pressing F2, F12, or Del during startup (check your motherboard manual for the exact key). Look for a setting called "Boot Mode," "UEFI/Legacy Boot," or "CSM" and change it to UEFI. Save and exit, then try booting again.

Do I need to convert my drive to GPT?

Only if your drive is larger than 2 TB, you're installing a modern operating system that requires it, or your motherboard only supports UEFI. If your current setup works and your drive is under 2 TB, MBR is fine. Check your motherboard manual or your operating system documentation to see if GPT is required for your hardware.

Can I convert just one partition instead of the whole drive?

No. MBR and GPT are drive-level formats, not partition-level. The conversion affects the entire drive. If you want to keep some data, move it to a different drive first.

How long does the conversion take?

The actual conversion command usually completes in seconds. If you're also reinstalling Windows, the whole process takes 30 minutes to an hour depending on your drive speed and internet connection for downloading Windows updates.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.