How to Convert Legacy BIOS to UEFI in Windows

In older versions of Windows, you were forced to reinstall the entire operating system if you wanted to convert legacy BIOS or Master Boot Record (MBR) to UEFI or GUID Partition Table (GPT). However, a new and simple tool called MBR2GPT was introduced in Windows 10. It lets you convert legacy BIOS to UEFI with just two commands.

Here is how you can convert legacy BIOS to UEFI in Windows 10. If you’re a Windows 11 user, you shouldn’t do anything, as UEFI mode is enabled by default on your device.

Do not skip any of the prerequisites of legacy BIOS to UEFI conversion mentioned below, as it can lead to system failure and even hardware issues in some cases.

Also read: How to Boot into UEFI Directly from Windows 10

Why Convert Legacy BIOS to UEFI?

You probably have some inkling why you’d want to change from the legacy BIOS to UEFI, but just to confirm, here’s what you need to know. Both BIOS and UEFI perform the same function on your PC – namely under-the-hood software integrated into your motherboard chip that lets you control various important low-level things.

Your BIOS/UEFI lets you control things like boot order, connected hardware, fan speeds, the physical lights on your computer and system time. Modern motherboards even let you undervolt and overclock your CPU! It’s powerful stuff.

UEFI is basically the new BIOS, performing the same job but better. With UEFI, you get faster boot times (ostensibly), higher drive capacities, better update methods and driver support, and a 64-bit mode (where BIOS is only 16-bit).

In other words, switching to UEFI is a bit of an upgrade and worth doing. Note that even modern computers (including Windows 11) tend to still call the motherboard software the BIOS, even if it’s technically UEFI.

Also read: How to Safely Bypass the TPM 2.0 Requirement in Windows 11

Prerequisites for Legacy BIOS to UEFI Conversion

There are many secondary requirements listed below for a flawless conversion. If you ignore any of these prerequisites, your Windows hardware may fail leading to a black screen. (Read the FAQ to know what options are available for you in case you encounter this problem.)

1. While there will be no data loss while converting legacy BIOS to UEFI, please back up your system as a precaution.
2. Always verify whether your Windows system is capable of supporting UEFI in the first place. Generally, all motherboards launched after 2014 are UEFI secure boot capable but that’s not always the case. So you should verify the eligibility for your device specifically.

To do so, use the Run command with the shortcut Win + R and type msinfo32 to launch the System Information window. In its right-hand side panel, check your BIOS Version/Date. If it says UEFI, your device is eligible for legacy BIOS to UEFI conversion. However, if it only gives the name of your BIOS version, the device does not have UEFI firmware settings. Trying to convert the legacy BIOS will lead to hardware failures.

3. You should be using Windows 10 v1703 or higher. If you are not sure, press Win + R, type winver and press Enter. On the second line, you should see “version 1703” or higher.

4. The disk you are trying to convert should not have more than three partitions. If you have more than three partitions on the Windows 10 installation drive, either merge or delete the excess partitions. Otherwise, you’ll encounter a “Disk Layout Validation Failed” error, which is fixable but best avoided.
5. If you are using BitLocker to encrypt your system, decrypt the drive and disable BitLocker protection before starting the conversion process. With BitLocker protection turned on, Windows 10 cannot convert your drive from legacy BIOS to UEFI.
6. After converting, you may have to change your motherboard firmware settings from legacy BIOS to UEFI. Depending on your motherboard manufacturer, the procedure to switch from one to the other will be different. Have your motherboard manual handy to make things easier for you.
7. Don’t proceed with the legacy BIOS to UEFI conversion if your Windows device is already on UEFI with secure boot enabled. We’ll show you how to check for this below.

If you want to know more, we have a full guide on the differences between UEFI and BIOS.

Also read: UEFI vs. BIOS: Which One You Should Use

Do I Need to Convert Legacy BIOS to UEFI in Windows 11?

If you’re using Windows 11, it means your device is past the milestone in switching from legacy BIOS to UEFI. This is because migrating to a UEFI secure boot is a mandatory Windows 11 compatibility requirement. There is no separate provisioning of legacy BIOS in Windows 11.

In rather simple words, Windows 11 doesn’t support legacy BIOS at all. If you want to install Windows 11 on an older Windows 10 device, you should first check whether that computer supports UEFI mode or not, and it should have a GPT partition, not MBR (check the following section for more details on this).

You can check this from a “Windows Security” option where “Secure boot” is displayed as On. Microsoft recommends you keep it that way to deter any malicious software from loading when the device is booting.

Also read: How to Install Windows 11 on Unsupported PCs (And Why You Shouldn’t)

The secure boot settings can also be verified from the BIOS options (called UEFI Firmware Settings) accessible in Windows 11 “Advanced startup.” After the BIOS screen shows up, navigate to the Boot Options tab. According to Microsoft, UEFI should be shown as the “first or only option.” This is especially true for Dell, HP, and Lenovo laptops. However, some other manufacturers may have continued to retain both UEFI and legacy/CSM.

Also read: The Ultimate Guide to Check Windows 11 Compatibility with Your PC

How to Check Whether You Are Using Legacy BIOS

Before you switch from legacy BIOS to UEFI in Windows 10, check whether you are actually using legacy BIOS. After all, there is no use converting if you are already on UEFI.

1. Search for “Create and format hard disk partitions” in the Start menu and press Enter to open the built-in Disk Management tool.
2. Right-click on the Windows installation disk, Disk 0, and select “Properties.”

3. In the Properties Window, go to the “Volumes” tab. If you see “Master Boot Record (MBR)” next to “Partition style,” you are on Legacy BIOS.
4. If, on the other hand, it says “GUID Partition Table (GPT)” as in the image below, then you’re already on UEFI and don’t need to do anything more!

Also read: The Differences Between MBR and GPT

How to Convert Legacy BIOS to UEFI

Once you’ve confirmed you are on legacy BIOS and have backed up your system, you can convert Legacy BIOS to UEFI.

1. Access Command Prompt from Windows’s advanced startup by pressing Win + X.
2. Go to “Shut down or sign out” and click on the “Restart” button while holding the Shift key.

3. The above action will reboot your system to the Advanced Startup screen.
4. Go to “Troubleshoot -> Advanced Options” and select the option “Command Prompt.”

5. Validate the disk you are trying to convert. Type the below command and press Enter.

mbr2gpt /validate

If you see the “Validation completed successfully” message, proceed to the next step. If you see any errors, your disk or system may not meet the conversion requirements.

If you have problems validating at this point, enter the following command. We highly recommend you use this add-on code to not lose data.

mbr2gpt /validate /allowFullOS

6. After validating the disk, execute the below command:

mbr2gpt /convert

As soon as you execute, Windows 10 will start the conversion process, i.e., add all the required UEFI boot files and GPT components, then update the Boot Configuration Data.

7. Restart your system, launch your motherboard firmware settings screen and change it from legacy BIOS to UEFI. The procedure to change from Legacy BIOS to UEFI depends on your motherboard manufacturer. Consult the manual for the exact steps.
8. After booting into Windows 10, you can verify whether or not you are converted. Just as before, open the disk properties window from the Disk Management tool and go to the “Volumes” tab. Here, you should see “GUID Partition Table (GPT)” next to “Partition style.”

Also read: How to Reset Your CMOS, and Why You Might Need To

How to Fix the MBR2GPT “Disk Layout Validation Failed” Error

While changing your hard drive from MBR to GPT, you may sometimes receive the error message: “MBR2GPT Disk layout validation failed for Disk#,” with the number # referring to your boot disk.

There are two reasons for this error: more than three partitions and no available space in C drive, the boot disk.

1. To solve the “Disk Layout Validation Failed” error, go to “Create and format hard disk partitions” from the search menu and check whether you have more than three partitions in the boot disk, Disk 0.
2. You need to “merge and delete” some of these extra partition volumes to bring down the number of partitions to three or less. Do create a backup of any important data in the extra partitions.

3. The second reason for the error is the Disk 0 drive not having enough space for an MBR to GPT conversion. To resolve this, you need to shrink its volume to anything between 200 MB to 2 GB.

Note: if your device is already on a GPT layout, these options will be greyed out.

Also read: How to Use ShadowExplorer to Restore Files from System Restore

Frequently Asked Questions

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Sayak Boral - Staff Writer

Sayak Boral is a technology writer with over eleven years of experience working in different industries including semiconductors, IoT, enterprise IT, telecommunications OSS/BSS, and network security. He has been writing for MakeTechEasier on a wide range of technical topics including Windows, Android, Internet, Hardware Guides, Browsers, Software Tools, and Product Reviews.