Solved: Unallocated Space Cannot Create Partition

If you find your unallocated space cannot create partition, you come to the right place. Here you can know the possible reasons and learn how to create a new partition on the unallocated disk space successfully and easily.


By Emily / Updated on April 1, 2024

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Why can’t create partition from unallocated space?

“Unallocated space cannot create partition in Disk Management”, “I cannot create new partition from unallocated space in Windows 8”... such kinds of problems appear commonly in a lot of forums. Why will this happen exactly?

Well, here, we find some reasons that might cause unallocated space not to create partition:

1. MBR and GPT
The top reason is that MBR (Master Bootable Record) supports the maximum capacity of 2TB only, up to four primary partitions or three primary partitions plus one extended partition. While GPT (GUID partition table) supports more than 2TB, almost unlimited number of partitions.

So, if you get the MBR disk over 2TB, the unallocated disk cannot create partition as normal. Check your disk size and format first when you cannot create new partition from unallocated space in Windows 10 via Disk Management.

2. There are some connected peripherals
Another reason for the Unallocated Space Cannot Create Partition error may be the peripheral devices connected to the system. Sometimes, Windows may assume these devices as the default hard disk and prevent you from creating a new one, especially if your hard disk is in MBR format.

3. Can't create inactive partition
It is also possible that a particular partition cannot be created because it is inactive. The active partition refers to the partition where the operating system is located. While inactive, the system will not be able to load that particular operating system.

How to successfully create partition on unallocated space on Windows 11/10?

For three reasons that we've mentioed above, we also prepare 3 ways to help you fix unallocated disk that cannot create partition. 

Method 1. Change MBR to GPT

To make the most use of unallocated space, you’re recommended to change MBR partition style to GPT partition style. Two ways are available here but please pay attention that not all hard drives fit GPT. Check it out in advance. 

▍ Option 1. Reinitialize MBR to GPT via Disk Management (Data Loss)

As Disk Management is one built-in tool in the Windows system, you can use it to reinitialize the disk to GPT. However, in this case, you need to erase the disk, which may lead to data loss. You could back up the MBR disk first while the whole process is too time-consuming. What’s more, there are many invisible files or folders that you can’t copy.

Option 2. Convert MBR to GPT via partition software (Data Safe)

Since changing MBR to GPT using Disk Management causes data loss,  it is a wise move to employ third-party partition software. In such cases, the AOMEI Partition Assistant Professional is one ideal choice. It helps you directly convert MBR to GPT without deleting any partitions or data and then perfectly solve the “unallocated space cannot create partition”  issue. Let’s see how it works.

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Step 1. Install and launch AOMEI Partition Assistant. Right-click the disk you need to convert. Select “Convert to GPT”.

Convert Data Disk To GPT

Step 2. A pop-up window will ask for your confirmation. Click “OK”.

OK To GPT Data Disk

Step 3. Then, click “Apply” to execute. Reboot will be required if there’s any running program.

Apply To GPT Data Disk

When the conversion is completed, you’re able to create a partition, extend partition with unallocated space, etc with Partition Assistant as well.

Method 2. Remove external devices

Since not being able to create a new partition may be caused by an external device like a USB or external storage device, if you are installing a new Windows, disconnect any peripherals connected to the system, except USBs that boot from Windows. For other external devices, you can just simply them.

Step 1. Open My Computer and find your external device by right-clicking "External Devices".

Step 2. Right-click on the external device and select "Eject" to safely remove the device from the system.

Eject external drive

Method 3. Active partition

An active partition is a partition that has an operating system. Usually there is only one such partition. However, a system may have partitions with multiple operating systems. In such cases, you need to define the partition as active so that the system can load the operating system from that partition at boot time. Without an active partition, the system cannot load after booting.

AOMEI Partition Assistant can also help you active partition quickly.

Step 1. Launch AOMEI Partition Assistant. Right-click on the partition you want to mark as active and select "Advanced" -> "Set Active Partition". 

Set active partition

Step 2. A reminderwill be presented in the main window. Click "OK".


Step 3. Click "Apply" to open the pending operations as shown in the screenshot below. You will get a reboot warning, click "Proceed" to start the operation.



To make the fullest use of the unallocated space on your hard drive, you can use it to create a new partition or extend other partitions with insufficient space. If you are reminded of errors like "unallocated space cannot create partition", you can try the methods mentioned in this post to fix it. Obviously, AOMEI Partition Assistant is the best solution. Compared with built-in tools in Windows, AOMEI software can solve the issue without data loss.

If you fail to create a new volume from unallocated space on Windows Server hard drive, you can try AOMEI Partition Assistant Server to solve it.

FAQs on unallocated space cannot create partition

Why is my hard drive unallocated or not initialized?

There are several factors that can cause an external hard drive to be marked as "Uninitialized" or "Unallocated." These include unexpected power interruption, improper insertion or removal, presence of bad sectors, physical damage, etc.

How to expand C drive with unallocated space?

To extend C drive in the Disk Management window, first right-click the C drive and select Extend Volume. This can be done by clicking Next in the Extend Volume Wizard. Then, select the desired amount of unallocated space to add to the C drive and click Next to continue.

How to create a partition from unallocated space using diskpart?

You can create a partition from unallocated space using the DiskPart command-line utility in Windows. Here's a step-by-step guide:

Step 1. Press Win + R and type cmd to open Command Prompt. Type diskpart and press Enter. This will open the DiskPart utility.

Step 2. Enter the following commands one by one: list disk > select disk X > create partition primary size=Y > assign letter=Z.

Step 3. Once the formatting is complete, type exit and press Enter to exit.

Emily · Staff Editor
Emily is an English editor of AOMEI Technology; she has a great passion for providing easy solutions for people to tackle with all disk or partition management problems. In addition to writing articles about disk/partition management, she also edits great tutorials on how to back up and restore disk for data security. In her spare time, she loves to learn computer skill to improve herself or stay with her family to enjoy a good day.