Resizing a partition lets you rebalance space on a drive, such as shrinking your C: drive to make room for a new partition, or growing C: when it’s running out of space. Windows 10’s built-in Disk Management tool can shrink and extend partitions without extra software, as long as you know its rules. This guide shows both, explains why Extend Volume is sometimes greyed out, and covers the recovery partition that often gets in the way.
Quick answer
Right-click Start and open Disk Management. Right-click a partition and choose Shrink Volume to make it smaller, or Extend Volume to make it bigger. Extending only works when there’s unallocated space directly to the right of the partition.
Before you start
- Back up important files. Resizing is usually safe, but a power cut or error during the process can cause data loss.
- Plug in your laptop so it doesn’t run out of battery mid-operation.
- Know your layout. In Disk Management, look at the bar for each disk. Partitions are shown left to right in the order they sit on the drive.
How to shrink a partition
- Right-click Start and choose Disk Management.
- Right-click the partition you want to make smaller, such as C:, and choose Shrink Volume.
- Windows calculates how much it can shrink. Enter the amount to shrink in MB. For example, 51200 MB is 50 GB.
- Click Shrink.
The freed space appears as Unallocated next to the partition. You can right-click it and choose New Simple Volume to create a new partition, or use it to extend another partition.
Why can’t I shrink more?
Windows can’t move certain system files, such as the page file, hibernation file, and System Restore data, so it stops shrinking at their location. To free more space, you can temporarily turn off hibernation (powercfg /h off in an admin Command Prompt) and System Restore, restart, shrink the partition, then turn them back on.
How to extend a partition
- Make sure there’s unallocated space immediately to the right of the partition you want to grow.
- Right-click the partition and choose Extend Volume.
- Click Next, choose how much of the unallocated space to add, and click Next again.
- Click Finish.
Why is Extend Volume greyed out?
- No unallocated space next to it. If the free space is on the far side of another partition, Windows can’t use it. You’d need to delete the partition in between (after backing it up) or use third-party partition software that can move partitions.
- A recovery partition is in the way. On many PCs, a small recovery partition sits right after C:, blocking it from growing. See the next section.
- The partition isn’t NTFS. Disk Management can only extend NTFS (and some ReFS) partitions.
If you want to combine two partitions into one, see how to merge partitions in Windows 10.
Resizing or moving the recovery partition
The recovery partition holds the Windows Recovery Environment, which you use to repair Windows when it won’t start. It’s usually 500 MB to 1 GB. Sometimes Windows updates need it to be larger, and sometimes it blocks C: from being extended.
Disk Management can’t resize or move a recovery partition. Microsoft documents a manual process: disable the recovery environment with reagentc /disable, use diskpart to shrink C: and delete and recreate the recovery partition, then re-enable it with reagentc /enable. Because one wrong diskpart command can erase the wrong partition, follow Microsoft’s official instructions exactly, or use a reputable partition tool, and only after a full backup.
Resize with diskpart (advanced)
You can also resize partitions from an admin Command Prompt. Run diskpart, then list volume, select volume X (replacing X with the number), and either shrink desired=10240 to shrink by 10 GB or extend to use adjacent unallocated space. Type exit when you’re done. Disk Management is easier and safer for most people.
After resizing
Restart your PC and open File Explorer to confirm the new sizes. If you created a new partition, give it a drive letter and a name in Disk Management.
Related: How to remove all partitions from a hard drive in Windows 10.
Related: Check SSD size in Windows 10.
Frequently asked questions
Will resizing a partition delete my files?
Shrinking and extending with Disk Management keeps your files. Deleting a partition does erase its data, so back up first.
How long does resizing take?
Usually a few seconds to a few minutes. Large drives with lots of data can take longer when shrinking.
Can I resize the C: drive while Windows is running?
Yes. Disk Management can shrink and extend the system drive while Windows is running.
Kermit Matthews runs Live2Tech from just outside Philadelphia. He is an IT specialist with over 20 years of experience, from a university help desk to small-business IT, IT management and his own consulting practice, and has written tech guides full time since 2020. Steps are checked against the current software on a real device or the maker’s official documentation. More about Kermit.