By Ailsa / Last Updated June 25, 2021

The Case

Hi guys, I just bought a laptop with a 1TB hard drive, there are just two partitions in Disk Management: one is a 910GB C partition, another is a Recovery partition. I am trying to create a new partition on my hard drive for other use. However, I can’t reduce the C partition size less than 455GB, I want to get a 100GB partition.

Why Do You Reduce Partition Size?

Reducing Partition size means decrease partition size on the existing partition. After shrinking volume, you will get an unallocated space. Thus, you can take advantage of the unallocated space to create a new partition for data storage, increase other partition (for example, extend the system partition to disable the low disk space warning on Windows computer), or create another partition to install another operating system like Linux or Windows.

Nowadays, Windows is capable of resizing partition in Disk Management, resize partition includes extend partition size and shrink partition size. How to reduce partition size in Windows 7/8/10?

Windows Shrink Partition with Disk Management

The following content are about reducing Windows 7 partition size in Disk Management:

  • Right click Computer on the desktop, choose Manage.

  • Select Storage>Disk Management.

  • Right click the partition that you want to reduce, select Shrink Volume.

  • Edit the proper size for the new partition, then click Shrink.

However, you can’t reduce the system partition beyond half its size in Disk Management. It’s the restriction in Disk Management. In other words, if your C drive is about 270GB and its free size is about 256GB, the available shrink size is about 132GB. You can’t shrink C drive to get an unallocated spaced more than 135GB. That’s why the problem appears in that case at the beginning.

Shrink Volume

On the other hand, if you reduce C partition size to get an unallocated space beyond half its size with DiskPart, you will get an error message that the parameter is incorrect. Therefore, if you want to get more unallocated space from system drive for other use, you may turn to other disk partitioning software for help.

Reduce Partition Size with AOMEI Partition Assistant

As the best free disk partitioning software-AOMEI Partition Assistant Standard can make up for the limitations of Disk Management and DiskPart command, which allows you to reduce partition size beyond its half size to fully use the free space. Here is how it works:

1. Free download AOMEI Partition Assistant Standard, install and run it.

2. Pitch on the partition you want to reduce, select Resize Partition.

Resize Partition

3. Slid the double arrow leftwards to reduce the partition size, you can only reduce its size to the used space.

Reduce Partition Size

4. Click Apply to reduce partition size for Windows 7/8/10 computer.


After a while, you will get an unallocated space, then you can create partition on it, or merge the unallocated space to other partition to extend partition size. Besides, AOMEI Partition Assistant has the ability to split partition, delete partition, recover deleted partition, create bootable media, and migrate OS to SSD drive, and more. For advanced users, you can try AOMEI Partition Assistant Professional edition.