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In Windows, “merging partitions” usually means extending an existing volume into unallocated space. Disk Management can do this only when the space is on the same disk, sits immediately to the right of the volume, and the volume uses NTFS or ReFS. If a partition is in between, the built-in tool cannot extend across it. Check the disk map before deleting, moving, or resizing anything.
Check whether Windows can extend the volume
Unallocated space is different from unused space inside a formatted partition. Windows can extend a volume into unallocated space; it does not simply combine a volume with free room that still belongs to another partition.
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- Open Disk Management by right-clicking Start and selecting Disk Management, or run
diskmgmt.mscas an administrator. Unallocated space appears with a black bar and the label Unallocated. See Microsoft’s volume-extension instructions and its Disk Management overview. - Read the disk map from left to right. Confirm that the target volume and unallocated space are on the same physical disk, and that the unallocated space is immediately after the target. Microsoft’s extension procedure supports NTFS and ReFS volumes.
- Check what lies between the volume you want to grow and the unallocated area. Even a small intervening partition prevents Disk Management from extending the target into that space.
Microsoft’s extension guidance applies to Windows 10 and 11 and Windows Server 2016, 2019, 2022, and 2025; the page was last updated June 11, 2025. For a disk larger than 2 TB to use capacity beyond 2 TB, Microsoft says it must use GPT.
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Extend a volume when the space is adjacent
Use Disk Management
- In Disk Management, right-click the volume you want to enlarge and select Extend Volume.
- Follow the Extend Volume Wizard. It defaults to adding all available adjacent unallocated space, but you can enter a smaller amount.
- Review the selection and finish the wizard. The volume should then show the increased capacity in Disk Management.
Use PowerShell as an administrator
PowerShell provides an alternative for a supported layout. Replace C with the drive letter of the volume you intend to extend:
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- SATA DRIVES ONLY — 2.5in & 3.5in: Works with SATA I/II/III hard drives and SSDs. Does NOT support IDE/PATA, M.2 NVMe, M.2 SATA, SAS, or drives already in a USB enclosure. Check your drive's connector before ordering — a bare SATA drive has a wide flat L-shaped edge connector, not a ribbon cable or a small M.2 gold-finger card.
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- 12V POWER ADAPTER INCLUDED — REQUIRED FOR 3.5in DRIVES: A 12V/2A AC power adapter is in the box and a wall outlet is needed. 3.5in HDDs cannot run on USB power alone — without the adapter the drive will fail to spin up or drop out during use. 2.5in drives are generally bus-powered, but the adapter is recommended for stability.
- PLUG AND PLAY, TOOL-FREE, HOT-SWAP: No drivers on Windows 10/11, macOS, or Linux. Lay-flat bay accepts a bare drive without tools, swaps without rebooting, and an LED shows power and activity. Note: S.M.A.R.T. diagnostics are not passed through the USB bridge, and on macOS a drive may need remounting after sleep. Drive not included.
$size = Get-PartitionSupportedSize -DriveLetter C
Resize-Partition -DriveLetter C -Size $size.SizeMaxThe first command reports the supported size range; the second grows the partition to its maximum supported size. Review the disk layout and confirm the drive letter before running the resize command.
What to do when another partition is in the way
If the unallocated region is not next to the target, Disk Management cannot extend the target across the intervening partition. Microsoft’s documented options are to remove that intervening volume, use a non-Microsoft partitioning tool that can move volumes, or leave the space separate and make a new volume there.
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| Option | When it fits | Main trade-off |
|---|---|---|
| Keep the space separate and create a new volume | You want to use the unallocated capacity without changing the existing partition layout. | The capacity remains a separate drive or volume rather than being added to the target. |
| Delete the intervening volume | You have confirmed it is expendable or have safely backed up its contents. | Deleting a volume deletes its files. Do not remove a recovery, EFI, or other system-related partition on the assumption that it is safe; the general extension procedure cannot establish what a particular computer needs. |
| Move a partition with a capable partitioning tool | You need the target and free space to become adjacent and the intervening partition must remain. | Moving partition boundaries carries data and boot risks; exact operations depend on the disk and partition layout. |
GParted’s hosted sample chapter describes moving a partition boundary so the unallocated space becomes adjacent before growing the target. It also notes that logical partitions inside an extended partition have additional boundary constraints. Its example is not a universal sequence for EFI, recovery, or other system partitions.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Back up and plan before moving or formatting
- Back up important files before moving a partition boundary. GParted characterizes this as a high-risk operation and warns that moving a partition can prevent an operating system from booting. Its hosted sample chapter says, “Before before performing this task, we highly recommend that you backup your data.”
- After resizing or moving a partition containing NTFS, GParted advises booting into Windows twice so Windows can run filesystem consistency checks.
- Formatting a volume destroys the data on that partition. Microsoft advises backing up files before formatting.
- Do not start by deleting or moving partitions simply to make the diagram look simpler. Confirm the target, the free space, and the role and contents of any partition between them first.
GParted’s cited guidance is a hosted sample chapter from Manage Partitions with GParted How-to, reproduced with permission from Packt Publishing. The general guidance cannot determine which partition is safe to move on an individual computer.
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SABRENT USB 3.0 Hard Drive Enclosure, 2.5/3.5in SATA HDD/SSD (EC-KSL3) | Tool-free; UASP; LED indicator; plug & play; 12V adapter incl.; Win/macOS/Linux; 3.5 hard drive enclosure
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