Error: Cannot Create EFI System Partition using MBR2GPT

Do you want to know why "cannot create EFI system partition" using MBR2GPT? This post will explain the reasons for you and provide some solutions.


By Dervish / Updated on October 13, 2023

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Why convert MBR to GPT?

As you know, GPT and MBR are two different disk types. Nowadays, people are more likely to use GPT disks because of their prominent advantages. According to the Windows 11 configuration requirements released by Microsoft, if users want to upgrade from Windows 10 to Windows 11, Windows 11 can only be booted from UEFI, which requires the system disk of Win 11 to be a GPT disk.

Compared with MBR disk, GPT disk has no limit on the size of the hard disk and can make full use of the hard disk space. What's more, GPT disks allow an almost unlimited number of partitions. You can have more than four primary partitions.

Cannot create EFI system partition using MBR2GPT.exe

If your disk is MBR style and you want to convert it to GPT, you can use MBR2GPT. MBR2GPT is a Windows built-in tool which first introduced in Windows 10 version 1703 (also known as the Creator's Update). MBR2GPT converts a disk from the Master Boot Record (MBR) to the GUID Partition Table (GPT) partition style without modifying or deleting data on the disk. This tool is available in both the full OS environment and Windows PE.

In most cases, MBR2GPT can run successfully. However, sometime, when you use MBR2GPT.exe to create an EFI system partition, you may receive this message: "Cannot create EFI system partition". This error may be caused by the following reasons:

1. The hard disk has more than 4 partitions.
2. There are many bad sectors on the disk.
3. The free space of the system disk is insufficient.

Later, I will show you how to solve these problems to successfully create an EFI system partition.

How to solve cannot create EFI system partition using MBR2GPT

I will provide you with a one-to-one solution for the above three reasons. Please follow the steps below.

▶ Solution 1. Delete or merge partition to reduce partition numbers 

If it is because the hard disk has more than 4 partitions, then we can delete partition to reduce the number of partitions. But deleting the partition will cause you to lose data, so you need to back up in advance. If you think this is too much trouble, you can also use AOMEI Partition Assistant Professional to merge partitions to reduce the number of partitions. This is a powerful disk partition management assistant, it can merge a partition with another partition into a larger partition without losing data. Please download the Demo Version to see how it works.

Download Demo Win 11/10/8.1/8/7/XP
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Step 1. Install and launch AOMEI Partition Assistant. Click the C drive and select "Advanced" > “Merge Partition” as the screenshot(You can also merge other partitions to reduce partitions).
Step 2. After this step, it will display the following picture and you can select the partitions you want to merge. Then, click “OK” to move on.
Step 3. Click Apply to submit the operation.

▶ Solution 2. Check bad sector

In addition, you can also use AOMEI Partition Assistant Professional to check for bad sectors and fix them with chkdsk.exe.
Choose a partition that you want to check, right-click it and choose "Advanced"> "Check Partition". Then, click check partition and fix errors in this partition by using chkdsk.exe. Finally, click Apply to submit the operation.

▶ Solution 3.  Extend partition space by allocating free space

If you receive "cannot create EFI system partition" using MBR2GPT, it is probably caused by insufficient free space in the system drive. We can add unallocated space on the disk to the system partition to extend size(If you receive an error message: "Cannot find room for the EFI system partition" is also for this reason). 

Similarly, we can use AOMEI Partition Assistant Professional to perform this operation. Right-click the partition which you want to allocate free space from and select "Allocate Free Space". Then, add it to partition C to extend the total capacity of partition C.

After troubleshooting these issues one by one, you can re-use MBR2GPT to create an EFI system partition.

What should you pay attention to when using MBR2GPT:
1. Although, MBR2GPT is available in the full OS environment, it is much better to use it in WinPE, because it is purer and more suitable for the conversion.
2. Before conversion, you should check if the version is 1703 or higher. You can Press Win + R and type winver to check the version.
3. Check if the disk is encrypted. If it is, unlock it.

Step 1. Run CMD as Administrator.

Step 2. Type mbr2gpt / convert / disk 0 / allowfullos and press Enter.

1. Before starting, you can type mbr2gpt / validate / disk:0 to check whether the disk meets the conversion requirements.
2. After Converting MBR to GPT, you should go to BIOS and then convert Legacy to UEFI mode.

A simple way to create EFI system partition

The above three methods can solve "Cannot create EFI system partition" using MBR2GPT. But if you think that using MBR2GPT to create an EFI system partition is too complicated, AOMEI Partition Assistant Professional can also help you. It can directly convert system partition from MBR to GPT without losing data quickly and easily. The detailed steps are as follows:

Step 1. Install AOMEI Partition Assistant and open the software.

Step 2. Right-click disk you need to convert and choose Convert to GPT or directly click the disk and choose Convert to GPT from the right column.

Convert 3tb Mbr Disk To Gpt

Step 3. Click OK to confirm you are going to convert MBR to GPT. At last, click Apply to save the operation.

Ok 3tb Disk

Apply 3tb

Tip: After the operation finishes, don’t forget to go to BIOS and change Legacy to UEFI.

With the help of AOMEI Partition Assistant, you can easily solve the issue: “cannot create EFI system partition using MBR2GPT”.  If you plan to convert MBR/GPT to MBR/GPT in Windows Server, please upgrade to AOMEI Partition Assistant Server.

FAQs about [Cannot create EFI system partition mbr2gpt]

1. What does the error message "Cannot create EFI system partition" during MBR2GPT conversion mean?
Encountering the "Cannot create EFI system partition" error while using the MBR2GPT tool signifies a problem when trying to convert a disk from Master Boot Record (MBR) to GUID Partition Table (GPT) format. Our article explains the underlying causes and provides solutions to overcome this error.

2. Can I proceed with the MBR2GPT conversion if I encounter the "Cannot create EFI system partition" error?
The "Cannot create EFI system partition" error can prevent successful conversion. Our article elaborates on why this error occurs and offers effective strategies to resolve it, allowing you to continue with the MBR2GPT conversion process.

3. Can I create EFI partition on MBR disk?
No, you cannot create an EFI (Extensible Firmware Interface) partition on an MBR (Master Boot Record) disk. EFI partitions are used in conjunction with GPT (GUID Partition Table) disks. GPT disks are a modern partitioning scheme that supports larger disk sizes, more partitions, and features like EFI booting.

Dervish · Staff Editor
Dervish is an English editor of AOMEI Technology; He is delicated to offering users easy and effecitve solutions for issuses related to disks and partitoins. In his spare time, he enjoy wathcning films, playing footable, traveling and so on.