By Cherry / Last Updated April 2, 2021

The Scenario

"Hi, I have a problem with partitioning my 4TB hard drive. I was trying to install the drive into a new PC, and I know Windows can’t be installed on a partition of more than 2TB, so I specifically installed a 140GB drive just for the OS. I was planning on using the 4TB drive for storage only. But I still can only create a 2TB partition on the 4TB drive! It won’t allow me to partition the rest of the unused space.”

Cannot Partition 4TB Hard Drive

Why cannot partition more than 2TB on 4TB hard drive?

As the scenario said, the user can’t partition more than 2TB on her 4TB hard drive. This isn’t an unusual scenario; many Windows users have encountered the same problem when upgrading their PCs. If you want to partition a 4TB hard drive, then you need to understand the basic requirements of hard drives in Windows.

Regardless of what Windows operating system you are using, you should know that there are two kinds of partition table on hard drives: Master boot record (MBR) and GUID partition table (GPT). MBR uses the standard BIOS, and supports drives up to 2TB in capacity. GPT uses UEFI (unified extensible firmware interface) which can support disks larger than 2TB. So, if you find that you can’t partition a 4TB hard drive, it could be because it is an MBR drive. If it is an MBR disk, then you can solve the problem by converting the drive from MBR to GPT.

Best way to partition 4TB hard drive in Windows 10, 8, 7

We already know that the MBR can only support disks up 2TB in size, any extra space beyond this will simply be invalid and will show as unallocated space. Although, you can normally partition unallocated space, you will find that the ‘New Simple Volume’ option is greyed out and you won’t be able to create a partition. Once you have checked to see whether your motherboard is UEFI compatible, you can proceed to converting your MBR disk to GPT and solve the 2TB limit problem.

Unfortunately, like with the ‘New Simple Volume’ function, Windows Disk Management will also grey out ‘Convert to GPT Disk’. That' s because the MBR contains some partitions, but Disk Management can only convert an empty disk to GPT or MBR. Namely, you need to delete all partitions before conversion.

Convert to GPT Greyed out

In order to convert an MBR disk to a GPT disk without losing any data or partitions, we highly recommend that you use AOMEI Partition Assistant Standard to convert the disk. AOMEI Partition Assistant is a professional disk manager that you can use to convert any disk between MBR and GPT in a few simple clicks without damaging any of your data.

Note: Although AOMEI Partition Assistant can help you convert from MBR to GPT without losing data, you should backup disk in advance to prevent any accidents causing data loss.

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Step1. Download, install and launch AOMEI Partition Assistant Standard edition. The basic information for your hard drive will be displayed in the main window. You will be able to see that the 4TB drive shows a 2TB partition and 2TB of unallocated space. In order to convert the drive from MBR to GPT you need to right click the MBR disk, select “Convert to GPT Disk”.

Convert 4TB to GPT

Step2. A window will popup asking you to confirm whether you want to convert the MBR disk to a GPT disk. Click OK, and you will be brought to the main window.


Step3. Here you can see that disk 2 has been marked as a GPT drive. In order to confirm this change, click Apply , and wait for the conversion to finish.

4tb Apply

Finally, the MBR disk will have been converted to a GPT disk and you will be able to partition the entire 4TB hard drive. If you would prefer to convert a system disk (a disk containing the OS) rather than a data disk, then you can upgrade to AOMEI Partition Assistant Professional edition which supports convert boot disk between MBR and GPT without losing data.

PS: if you want to convert a boot disk from MBR to GPT, then you need to make sure that your computers motherboard supports UEFI mode, otherwise, the computer won’t boot up after the hard drive conversion has finished.