How much is the MBR Maximum Disk Size and How to Make It Bigger?

4 TB hard drive only shows 2 TB? This is because the hard disk size is limited by the MBR maximum disk size. This article will introduce you to the basic information of MBR and show you how to break the MBR size limit.


By Dervish / Updated on May 12, 2023

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What do MBR mean?

MBR (Master Boot Record) is an old disk partition style that is used to store data on HDD/SSD. If the partition style of the disk was set to MBR disk when it is initialized, the MBR partition style also determines the maximum size of the hard disk.

MBR disk can only be divided into 4 primary partitions or 3 primary partitions + 1 extended partition, and the MBR maximum disk size is 2T. If your hard disk exceeds 2T, the excess part will be displayed as “unallocated” in the Disk Management, and you will not be able to view and access it in the file explorer.

Why is MBR partition system limited to 2 TB disks?

In general, the hard disk uses 512-byte sectors. So, I use a 512-byte sector as an example to calculate the MBR max size:

In MBR, the size limit of the disk is related to the number of addressing bits, and the storage addressing of MBR is 32 bits. Therefore, the address range of the hard disk is equal to 2^32 = 4G.

Because the sector is 512 bytes. Therefore, the capacity of the MBR Disk should be 4G * 512 Bytes = 2 TB.

How do I break the MBR partition size limit?

From the first two paragraphs, we have drawn the conclusion of the MBR maximum disk size. You may be thinking, “Since MBR disk has a 2T size limit, is there any way I can use a hard disk larger than 2T?” Don’t worry, I will introduce you to another partition style.

GPT (GUID Partition Table) is a new partition style. Not only does it have no size limit, but it can also be infinitely partitioned on a single drive. The following are the main differences between MBR and GPT:

☞ MBR disk can only be divided into 4 primary partitions or 3 primary partitions + 1 extended partition, and the MBR maximum disk size is 2T. GPT has no limitation on partition and hard drive capacity. (Windows supports up to 128 partitions)
☞ MBR hard drive has better compatibility with the Windows system, and GPT is slightly worse.
☞ MBR disk is booted by BIOS, and GPT is booted by UEFI.
☞ GPT partitioned disks have redundant primary and backup partition tables for improved partition data structure integrity.

Since GPT has no size limit, in order to get more space, we need to convert the MBR partition style to GPT. The GPT partition style will gradually become the mainstream in the future. Microsoft's newly released Windows 11 clearly stated that when you upgrade from Windows 10 to Windows 11, Windows 11 needs to boot from UEFI, which requires the system disk to be a GPT disk.

How to convert MBR to GPT to get a larger size without losing data

To convert MBR to GPT, you need a reliable software. I recommend you to use AOMEI Partition Assistant Professional, this is a market-leading disk management utility that supports Windows 11, 10, 8, 7, Vista, XP users. It can convert the disk from MBR to GPT without losing data, and the converted disk can be used normally. More importantly, its operation is very simple. It only takes three simple steps to convert successfully, that is why I strongly recommend it.

In addition, if you want to convert the file system of the hard drive from NTFS to FAT32 or convert primary partition to logical drive, it also can solve it for you.

Download Demo Win 11/10/8.1/8/7/XP
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Note: If you want to convert the system disk from MBR to GPT, please make sure that your motherboard supports UEFI boot mode, otherwise the computer will not boot normally!

Step 1. Install and run AOMEI Partition Assistant Professional. Right-click the disk (take the system disk as an example) and choose “Convert to GPT”.

Step 2. Click “OK” and “Yes” to confirm your operation.

Step 3. Click “Apply” to commit the pending operation.

Now, you have successfully converted MBR to GPT. If you are converting a system disk, you need to change the BIOS to UEFI after conversion.


Sum up

This is the whole process of breaking through the MBR maximum disk size. With AOMEI Partition Assistant Professional, everything becomes easy. If you want to use it in Windows Server, please upgrade to Server edition.

Dervish · Staff Editor
Dervish is an English editor of AOMEI Technology; He is delicated to offering users easy and effecitve solutions for issuses related to disks and partitoins. In his spare time, he enjoy wathcning films, playing footable, traveling and so on.