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The partition table GUID (GPT) was introduced as part of the Unified Extensible Firmware Interface (UEFI). GPT offers more options than the traditional MBR partitioning method commonly used in PCs. If you have a large hard disk, you can convert MBR to GPT. This is because MBR disks only support four partition table entries. If you want more partitions, you must create a secondary structure called an extended partition.
So for each hard disk over 2 TB, we must use a GPT partition. If you have a hard disk larger than 2 TB, the remaining disk space will not be used unless you convert it to GPT. The number of partitions on a GPT disk is not limited by temporary schemes, such as container partitions defined by the MBR Extended Boot Record (EBR).
Here is an image of the basic reader that explains the GPT format.
Remember that it will also protect the MBR zone for backward compatibility. See chapter 5 of the Unified Extensible Firmware Interface (UEFI) specification (version 2.3) for more information about GPT.
Convert MBR to GPT
One of the biggest challenges in converting MBR to GPT is that converting MBR to GPT is only possible if there are no partitions or volumes on the disk – making conversion without data loss impossible. I still don’t know why Microsoft hasn’t offered a simpler solution to this problem. Fortunately, there are several solutions that can help you convert MBR to GPT without data loss.
Before you begin, it is always a good idea to back up your data in a safe place first.
1. convert MBR to GPT with the disk part
Save all your data and then use the DISKPART command.
- Open the command prompt and type DISKPART and press Enter.
- Then type list disk (Note the number of the hard disk you want to convert to GPT)
- Then type select disk disk number.
- Finally, enter convert gpt.
2) Convert MBR to GPT without data loss with Gptgen
You can convert MBR to GPT without data loss – using a command line program called gptgen Gptgen is a tool designed to non-destructively convert disks that are typically partitioned in an MSDOS MBR system (including extended partitions) to use a GUID partition table (GPT).
It is a very comprehensive tool, but somewhat complicated to use. According to the tool’read me’ file, the tool syntax is gptgen[-w].physicaldriveX, where X is the disk number reported by the disk management console or the list disk command of the DISKPART utility. The switch -w allows gptgen to write the generated GUID partition tables to disk – otherwise the primary table is written to a file named primary.img and the secondary table in secondary.img is written to the directory from which the program was called. You can then write the tables to disk with ddd.
3. convert MBR to GPT without data loss with Partition Wizard
The last method is to use a tool called AOMEI Partition Assistant Lite Edition. It is a free multi-function partition management software. This tool can help you convert a hard disk containing data to GPT or MBR style without data loss.
NOTE: It seems that the free version of the partition wizard does not allow the conversion of MBR to GPT.
To convert a disc to MBR/GPT disc:
- Select the disc to convert ;
- Right-click the disc and select Convert to GPT/MBR disc.
- Confirm your operation by clicking OK to continue;
- Click the Apply button on the toolbar to apply the changes.
If you know of another method to safely hide the MBR from GPT, please let us know during the comment session.
UPDATE: Learn more about the new MBR2GPT Disk Conversion Tool in Windows 10 Creators Update v1703, an integrated tool that allows you to safely and without destruction convert a Windows 10 computer from an old BIOS to UEFI disk partitioning.