Before you start
- Administrator access
- Free space on the partition you want to shrink
- A backup of important files
Method 1 Shrink an existing partition
Leave at least 20–30% of C: free after shrinking so Windows has room for updates.
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Step 1: Open Disk Management
Right-click the Start button and choose Disk Management (or press Win + R and type diskmgmt.msc).
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Step 2: Choose Shrink Volume
Right-click the partition you want to split (usually C:) and select Shrink Volume.
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Step 3: Enter the size
Windows shows the maximum it can shrink. Enter the amount for the new partition in MB (1 GB = 1024 MB). For example, 102400 for 100 GB.
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Step 4: Click Shrink
Click Shrink. A black bar labelled Unallocated appears.
Method 2 Create the new partition
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Step 1: Start the wizard
Right-click the Unallocated space and choose New Simple Volume.
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Step 2: Choose size and letter
Keep the full size (or enter less), and pick a drive letter, for example D:.
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Step 3: Format the new partition
Choose NTFS, give it a name like “Data”, keep Perform a quick format ticked and finish. Only the new, empty space is formatted; your existing files are untouched.
Why can’t I shrink more?
Windows can’t move certain system files (page file, hibernation file, restore points), so it may offer less space than you expect. To free more: temporarily turn off System Protection, run powercfg /h off to disable hibernation, and set the page file to No paging file, restart, shrink, then turn them back on. Third-party partition tools can move these files, but always back up first.
Troubleshooting
Shrink Volume is greyed out
The partition may not be NTFS, or it’s a recovery or system partition. Choose your main data partition.
The new partition isn’t visible in File Explorer
It needs a drive letter. Right-click it in Disk Management > Change Drive Letter and Paths > Add.
BitLocker is on
Shrinking works with BitLocker, but suspend protection first if you run into errors.
Frequently asked questions
Will partitioning delete my files?
No. Shrinking keeps your files; only the new partition is formatted.
Can I merge the partitions later?
Yes: delete the new partition (after copying its files), then right-click C: and choose Extend Volume. Extend only works with space directly to the right.
Is it better to use separate partitions?
It can keep data separate from Windows, but backups protect you far better than partitions. A second physical drive is even better.
Summary
Open Disk Management, right-click your partition, choose Shrink Volume, then turn the unallocated space into a New Simple Volume. Your existing files stay where they are; just back up first.
