Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →The simplest way to divide hard disk space in Windows 11 is to shrink an existing volume in Disk Management, then use the newly created unallocated space for another volume. You do not need to format the existing partition first.
This method works for eligible basic volumes when you have administrator access. Microsoft says Disk Management looks and works the same in Windows 10 and Windows 11.
What “dividing disk space” means in Windows 11
In normal Windows terminology, this usually means splitting one existing volume into two. For example, you might reduce a 1 TB C: drive to 700 GB and create a new 300 GB D: drive.
There are two different kinds of free space to distinguish:
#1 Best Overall
- Easily store and access 2TB to content on the go with the Seagate Portable Drive, a USB external hard drive
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
| Type | Where it is | What you can do with it |
|---|---|---|
| Free space | Inside an existing volume, such as C: | Store files, but it is not a separate partition |
| Unallocated space | Belongs to no volume and appears separately in Disk Management | Create a new volume or extend an eligible existing one |
Disk Management displays unallocated space with a black bar and the label Unallocated. The process below converts some free space inside an existing volume into unallocated space, then creates a new volume from it.
Before you begin
- Back up important files before changing partition sizes. A power failure, disk problem, or mistake involving the wrong volume can make data inaccessible.
- Make sure the volume has enough free space for the split. File Explorer’s free-space figure is only a starting point; Windows may be unable to shrink the volume by all of that amount.
- Do not delete or format a volume unless you are certain it contains no required data. Formatting destroys the data on that partition, and deleting a volume deletes both the volume and its data.
- Use an administrator account. Disk Management operations require administrative permissions.
Open Disk Management
Use any of these methods:
- Right-click the Start button and select Disk Management.
- Open Search, type Disk Management, and select Create and format hard disk partitions.
- Press Windows + R, enter diskmgmt.msc, and select OK.
- Open Computer Management, then go to Storage > Disk Management.
For an elevated launch, search for diskmgmt.msc, right-click it, and choose Run as administrator.
How to divide a hard drive using Disk Management
1. Identify the volume to shrink
In the lower section of Disk Management, find the correct physical disk and volume. Check the drive letter, capacity, and volume label carefully. If you want to divide your main Windows drive, this is normally the volume labeled C:.
Do not confuse a second volume on the same disk with a separate physical disk. The disk labels on the left—such as Disk 0 and Disk 1—identify physical drives. The sections to the right represent volumes or partitions.
Recommended Free Tools
2. Shrink the existing volume
- Right-click the volume you want to reduce.
- Select Shrink Volume.
- Wait while Windows queries the volume.
- In Enter the amount of space to shrink in MB, enter the amount to remove from the existing volume.
- Select Shrink.
Windows creates the new space at the end of the selected volume as contiguous unallocated space. Ordinary files are relocated automatically, so shrinking does not require reformatting.
The amount is entered in megabytes. As a practical conversion, 1 GB is approximately 1,024 MB:
Rank #2
- Easily store and access 5TB of content on the go with the Seagate portable drive, a USB external hard Drive
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
| Approximate new space | Enter in the shrink box |
|---|---|
| 50 GB | 51,200 MB |
| 100 GB | 102,400 MB |
| 200 GB | 204,800 MB |
After shrinking, the original volume becomes smaller and a black-bar section labeled Unallocated appears immediately to its right.
3. Create a new volume from the unallocated space
- Right-click the black-bar Unallocated area.
- Select New Simple Volume.
- In the New Simple Volume Wizard, select Next.
- Enter the volume size in MB, or accept the maximum size, then select Next.
- Accept the suggested drive letter or choose another available letter, then select Next.
- At Format Partition, choose Do not format this volume if you intend to format it later, or accept the default formatting and select Next.
- Review the settings and select Finish.
If you accept formatting in the wizard, Windows creates a usable file system on the new volume. The new drive then appears in File Explorer with its assigned letter.
Free tools Windows power users keep installed
One-click scans. No signup required.
Example: split a 1 TB Windows drive
Suppose Disk Management shows a 1 TB C: volume and you want a separate data drive of approximately 200 GB:
- Right-click C: and select Shrink Volume.
- Enter 204800 MB.
- Select Shrink.
- Right-click the resulting unallocated space and select New Simple Volume.
- Use the maximum available size, assign a drive letter such as D:, and complete the wizard.
This leaves approximately 800 GB in C: and creates a separate volume of approximately 200 GB. Actual displayed capacities may differ because Windows and drive manufacturers calculate storage differently.
Why Windows may not let you shrink by the amount you want
Windows does not base the maximum shrink amount solely on the free-space number shown in File Explorer. Certain unmovable files can establish the point beyond which Disk Management cannot shrink the volume.
Microsoft specifically identifies the paging file and shadow-copy storage area as possible blockers. A volume may show substantial free space while offering a much smaller shrink amount.
Rank #3
- Easily store and access 1TB to content on the go with the Seagate Portable Drive, a USB external hard drive.Specific uses: Personal
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop. Reformatting may be required for Mac
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
If shrinking fails or the available amount is unexpectedly small:
- Check the Application log in Event Viewer for Event ID 259. Microsoft uses this event to identify an unmovable file.
- Microsoft also documents fsutil volume querycluster /? for investigating the file associated with blocking clusters.
- In some cases, temporarily moving the paging file or deleting stored shadow copies allows the volume to be shrunk. Restore the relevant settings afterward.
Do not use this process casually on a raw partition containing application data, such as a database file. Microsoft warns that shrinking such a partition may cause data loss. A high number of bad clusters can also prevent shrinking; in that situation, move the data and replace the disk rather than relying on block-level copying.
How to extend a volume after dividing space
You may later want to give space back to the original volume. Disk Management can extend a basic volume only when all of these conditions are met:
- The unallocated space is immediately after the target volume—in the graphical view, directly to its right.
- The unallocated space is on the same physical disk.
- The volume uses NTFS or ReFS.
- On a disk larger than 2 TB, the disk uses GPT to address space beyond 2 TB.
To extend it, right-click the volume, select Extend Volume, and complete the wizard:
- Select Next.
- Under Select Disks, specify how much available space to use. The default is Maximum available.
- Select Next, then Finish.
For example, if you shrink C: and immediately create a new volume from the unallocated space, that space is no longer available to extend C:. To extend C:, the space must again be unallocated and directly adjacent to it.
Why “Extend Volume” is greyed out
The most common cause is the position of the unallocated space. If another partition sits between the volume and the unallocated space, Disk Management cannot move that partition and cannot extend the target volume through this procedure.
Rank #4
- Easily store and access 4TB of content on the go with the Seagate Portable Drive, a USB external hard drive.Specific uses: Personal
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
Other documented causes include insufficient permissions, an unsupported file system, or an incompatible partitioning scheme. Windows’ built-in tool does not move partitions to rearrange them. Your choices are to delete the intervening volume after backing up its data, use a non-Microsoft partitioning application that can move volumes, or create a separate volume instead.
Optional command-line method: DiskPart
DiskPart can perform similar operations, but it is easier to select the wrong disk or volume. Use it only after checking the numbers carefully. Open Command Prompt as administrator, then run:
The Tool Desk
Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →diskpart
list volume
select volume <volume-number>
shrink desired=<desired-size>
list disk
select disk <disk-number>
create partition primary
format fs=ntfs label=Backup quick
Replace the values in angle brackets with actual numbers. The desired value is in MB. The shrink command also supports a fallback minimum:
shrink desired=<desired-size> minimum=<minimum-size>
DiskPart commands act on the object currently in focus. Always run list volume or list disk and then select the intended object before modifying it.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Formatting warnings
Formatting an existing volume is not part of the normal shrinking process. If you right-click an existing volume and select Format, Windows warns that formatting destroys the data on that partition. Windows also cannot format a disk or partition that is currently in use, including the partition containing Windows.
What’s actually slowing this PC down?
Pick the symptom - the matching free tool is one click away.
Best Value
- [Upgraded Version] - This external hard drive features a mirrored logo stripe combined with a striped anti-slip design, and the rounded corners of the casing make it easier to grip. The stripes also have a heat dissipation function, ensuring stable and fast data transfer.
- 【Ultra-thin and quiet】 - The motherboard adopts JMicron 578 noise-free solution, giving you a quiet working environment. Lightweight and portable size designed to fit in your pocket for easy portability.
- 【Ultra-Fast Data Transfers】 - Pairing this external hard drive with JMicron 578 solution USB 3.0 and USB 2.0 interfaces enables blazing-fast data transfer. It boasts theoretical read speeds of up to 125MB/s and write speeds of up to 103MB/s.
- 【Plug and Play】 - With no software to install, just plug it in and the drive is ready to use.The hard disk chip is wrapped with an aluminum anti-interference layer to increase heat dissipation and protect data.
- 【What You Get】 - 1 x Portable Hard Drive, 1 x USB 3.0 Cable, 1 x User Manual, Gift-type shell packaging ,Three-year manufacturer's warranty and free technical support services.
A quick format creates a new file table but does not fully overwrite or erase the volume. A normal format fully erases existing data and takes longer. Therefore, quick format should not be treated as a secure data-erasure method.
Common mistakes to avoid
| Mistake | Correct approach |
|---|---|
| Formatting before shrinking | Right-click the existing volume and use Shrink Volume; reformatting is not required. |
| Assuming File Explorer free space is unallocated space | Use Disk Management to create black-bar unallocated space first. |
| Expecting Windows to extend into any nearby space | The space must be immediately to the right, on the same physical disk. |
| Using quick format to securely erase data | Use a proper secure-erasure procedure; quick format does not fully overwrite the volume. |
| Choosing the wrong disk or volume in DiskPart | Check list disk and list volume before every destructive operation. |
FAQ
Can I partition a Windows 11 drive without losing files?
Shrinking an NTFS basic volume normally preserves its files and does not require reformatting. Back up important data first, because partition operations can still be affected by disk faults, power loss, or user error.
How much space should I leave on the Windows drive?
There is no single Microsoft-required amount in the documented Disk Management procedure. Leave enough room for Windows, installed applications, updates, and your normal working files. Disk Management will only offer the amount it can safely shrink.
Can I split a drive without installing software?
Yes. Disk Management is built into Windows 11 and can shrink a basic volume and create a New Simple Volume from the resulting unallocated space.
Why is the Shrink Volume option unavailable?
The selected item may not be a supported basic volume, you may lack administrator permissions, or Windows may be unable to perform the operation on that volume. NTFS and unformatted basic volumes are supported for shrinking.
Can I merge two partitions with Disk Management?
You can extend a volume only into immediately adjacent unallocated space on the same physical disk, and the volume must use NTFS or ReFS. Disk Management cannot move an intervening partition.
The Bottom Line
For most Windows 11 PCs, use Disk Management: right-click the existing volume, select Shrink Volume, enter the amount in MB, and then create a New Simple Volume from the black-bar unallocated space. Do not format the original volume first, and back up important data before changing the disk layout.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
