By AOMEI / Last Updated September 3, 2019

Can’t extend partition with an unallocated space

“My computer is running Windows 10. Recently, I’m always prompted by Low Disk Space warning and I find that my primary partition almost full. After getting an unallocated space by shrinking another partition, I try to extend C drive but only find that Extend Volume greyed out. What happens? How can I extend partition in Windows with unallocated space? ”

Why Extend Volume Greyed out in Windows 10?

You may need to extend partition, especially system partition due to the low disk space caused by caches, temporary files, or other reasons.

Extend partition is not a bad choice to solve Low Disk Space warning. When it comes to extending partition, the first idea occurs to you might be using Disk Management. But you can extend partition in Disk Management only when there is an unallocated space adjacent behind the partition. Otherwise, Extend Volume will be greyed out just as the following screenshot shows.

You’ll need to delete the partition behind between the partition that you want to extend and the unalclaoted space, if you want to extend partition with the unallocated space, as you are not allowed to move partition with Disk Management in Windows 10. If you don’t want to suffer from data loss, you need to back up data before partition deletion.

Extend Partition without deleting

What if you don’t want to delete partition? Don’t worry, you can turn to AOMEI Partition Assistant Professional, which is specialized in partition management. It enables you to extend partition no matter there is unallocated space adjacent to the partition you try to extend or not.

And this software works perfectly on Windows 10/8.1/8/7, XP or Vista. Besides, with the friendly-use interface, you can easily finish the task.

Install AOMEI Partition Assistant and refer to the detail steps presented as follows:

PS.: You can also download Demo version of AOMEI Partition Assistant Pro to have a try at first.

Extend partition with non-contiguous unallocated space

Before you do:

  • This operation may change the original location of your data, so we suggest you to learn the tutorial “How to Safely Partition” before executing this operation.

  • If the partition has running applications, AOMEI Partition Assistant will suggest you to close them or perform the operation under PreOS Mode.

Step1. Run AOMEI Partition Assistant Professional, right click the partition you want to extend (eg. partition C) and then choose Merge Partitions.

Merge Partitions

Step2. Select Extend system partition and then click Next.

Add Unallocated Space to C Drive

Step3. You can preview the operations, before click Apply to perform them.

Apply Merge


  • Only 2 partitions can be merged at one time, moreover the two partitions must be adjacent. However, you can merge two or more parts of unallocated space into a partition and the unallocated space just need to be behind the partition, whether it is adjust to the partition or not.

  • You can merge data partition into system boot drive, but you cannot merge system boot drive into data partition.

  • "System Reserved" partition could not be merged.

Extend partition without unallocated space

Step1. Run, install and launch it. Choose Extend Partition Wizard on the left of the interface.

All Tools

Step2. Select Extend system partition and then click Next.

Extend Partition Method

Step3. Choose the partition you want to transfer free space from (partition D) and then click Next.

Select Partitions

Step4: Right move the bar to make sure how much size you want to add into system partition and click Next.

Extend Size

Step5. Click Proceed to perform the operations then you can extend system partition.


Besides the two methods mentioned above that can help you solve the problem of “extend volume greyed out in Windows 10”, you can also extend partition through allocating free space from another partition to the partition you need to extend. AOMEI Partition Assistant Professional allows you to manage partitions more completely.