By Emily / Last Updated May 12, 2023

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, it might have something to do with the formats of hard disk - MBR and GPT.

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.

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

In order 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 such as Windows XP, etc! Check it out in advance. 

Method 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.

Method 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.


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.