By AOMEI / Last Updated May 15, 2020

What does this mean?

Some people who try to upgrade to Windows 10/8 may get an error saying “Windows needs more space”. It also states that how much space on the drive C: you need for the upgrade. The computers with hard drive relatively small or low free disk space are more likely to meet this error. Windows upgrade needs some free space to create a backup of the previous system to ensure that it can go back to the original system if the Windows upgrade fails. Therefore, you will receive this error when the upgrade program detects there is not enough space on the system drive. However, in some other cases, you will also get this Windows needs more space to upgrade error when there is enough free space left on C: drive.

Windows Update Error

How much space does windows 10/8 take?

According to Microsoft, space required for Windows 10/8 upgrade is 16 GB for 32-bit OS and 20 GB for 64-bit OS. As mentioned, the upgrade program will have to make a backup of the current OS, so if your current operating system is very large, then Windows 10 needs more space than 20GB.

Possible solutions

As the Windows needs more space in Windows 10 upgrade suggets, you can either use Disk Cleanup to free up space on C: drive or use another drive or external drive to store the backup of the previous Windows system. If both options are not practical for you, you can try the third one to extend C drive in Windows 7 with free space of another partition. As you may know, the Windows built-in tool Disk Management can extend a partition only when there is contiguous unallocated space right behind it. The problem is that there is no contiguous unallocated space behind system drive in most of the cases. Therefore, you need to use free third party disk partition software like AOMEI Partition Assistant Standard.

To extend system partition:

1. Download and run AOMEI Partition Assistant.

2. Right click on a partition on the same hard drive with system partition that has enough free space, and select "Resize/Move partition".

Resize Partition

3. In a new pop-out window, drag the partition’s end leftwards to shrink this partition to generate some unallocated space.

Shrink Partition

4. Right click C: drive and select “Merge Partition”, and in a pop-out window, check C: drive and the unallocated space, and click “OK”.

Select Unallocated Space

5. Then you can see the unallocated space has been added to C: drive. If you do not need other operations, click "Apply" to finish the job.


If you have extend the system partition enough, you should never meet the Windows needs more space error. Besides “Merge Partition”, you can also use “Move Partition” and “Resize Partition” toextend system partition before upgrading to Windows 10.