By AOMEI / Last Updated June 24, 2021

Why can’t create partition from unallocated space?

“Unallocated space cannot create a 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 with 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 rest of the unallocated space will be out of control and cannot be used to create a new partition as normal. Check your disk size and format first when you cannot create a new simple volume from an unallocated space in Disk Management.

How to successfully create partition on unallocated space?

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 “unallocated space cannot create partition”  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 Disk”.

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 conversion is completed, you’re able to create partition, extend partition with unallocated space and so on with Partition Assistant as well.