Use 'Disk Management' to Shrink a Volume in Windows

What Shrinking a Volume Does

Shrinking a volume takes free space from the end of an existing partition and converts it to unallocated space, without touching the files already stored on the rest of the partition. That unallocated space can then become a new partition — for a second OS in a dual-boot setup, a dedicated media library, or just a separate logical drive for organization. It's non-destructive to your existing data as long as you don't shrink below what's actually in use, but you should still back up first, since any disk operation carries some risk if interrupted.

Step 1: Open Disk Management

Right-click the Start button and choose Disk Management (or press Win + R, type diskmgmt.msc, and press Enter).

Step 2: Shrink the Volume

1. In the graphical view at the bottom, right-click the partition you want to shrink (commonly C:) and choose Shrink Volume....
2. Windows takes a moment to calculate the maximum amount it can shrink by, then shows a dialog with three fields:
   • Total size before shrink in MB — the current partition size.
   • Size of available shrink space in MB — the maximum Windows calculated it can free up.
   • Enter the amount of space to shrink in MB — this is the only field you edit. Enter how much space you want to free up, in megabytes (e.g. type 102400 to free up 100GB).
3. Click Shrink. The operation runs quickly for most drives and completes in a few seconds to a couple of minutes.

Why the Available Shrink Space Is Sometimes Much Smaller Than Expected

This trips people up constantly: Disk Management might show you have 400GB free in File Explorer, but the "available shrink space" field only offers 50GB. This happens because Windows can only shrink a volume up to the point of the last movable file — it will not relocate files during a shrink operation. Common causes of an artificially small shrink limit:

• Unmovable system files near the end of the partition, such as the page file, hibernation file, or System Restore snapshots.
• File fragmentation — files scattered near the physical end of the volume block further shrinking even if there's technically enough total free space.

To fix this before shrinking:

1. Temporarily disable the page file: Settings > System > About > Advanced system settings > Advanced tab > Performance Settings > Advanced tab > Virtual memory Change, uncheck Automatically manage paging file size for all drives, select the drive, choose No paging file, and click Set. Reboot.
2. Disable System Restore temporarily, or reduce its allocated disk space, under System Properties > System Protection.
3. Run Disk Defragmenter (search "Defragment and Optimize Drives") on the target volume — even on an SSD this can consolidate metadata enough to unlock more shrinkable space (this is a rare legitimate reason to defrag an SSD; Windows normally avoids doing this automatically for SSD longevity).
4. Reopen Disk Management and try Shrink Volume again — the available space figure should now be much closer to your actual free space.

Step 3: Use the New Unallocated Space

After shrinking, you'll see a black Unallocated block next to your shrunk partition in Disk Management. From here:

• Right-click it and choose New Simple Volume to format it as a new drive letter for data.
• Leave it unallocated if you're about to install a second OS for dual-boot — the other OS's installer will claim it during setup.

When Disk Management Can't Shrink Enough

If even after clearing the page file and hibernation file the shrinkable amount is still far short of your free space, a third-party partition tool like MiniTool Partition Wizard or EaseUS Partition Master (both offer free tiers) can perform a shrink that includes relocating files, something Disk Management deliberately won't do on its own. These tools carry more risk since they actively move data during the operation, so back up first if you go this route.