Modifying Size of a Mac Partition without Data Loss

mac-clean-data-iconDisk Utility in Mac OS X is a complete disk management software that facilitates creating a new partition on the hard drive utilizing available free space, modifying existing partitions, and deleting Mac volumes efficiently. Every Mac volume has a set of associated permissions maintaining integrity of the file system on the drive. User needs to repair this set of permissions whenever any volume throws some exception. Disk Utility facilitates checking and repairing both disk and the set of associated permissions for every individual Mac volume, if you face any disk related issue.

People partition a hard drive to store different types of data separately, or modify Mac partition size under the circumstances, such as when they need to create new one for dual boot.

It is often seen that many users go for a boot camp partition (Windows installation on a Mac volume) and hence need a separate empty disk; a separate volume acts like a separate disk. If a partition is available with required free size, you can use it, else you have to trim one or more existing volumes to create a new one for OS installation.

Though modifying a partition in Mac OS X is not much difficult, user must be familiar with the Disk Utility and the steps to be followed during the process. However, those who are not aware of the Disk Utility and how to do such modifications can opt for some professional software with a simple GUI available on the Internet.

Let us go through a few simple steps to modify Mac partition using Disk Utility:

  • Launch Disk Utility

(Go to task bar and follow Go-> Applications-> Utility folder-> Disk Utility)

  • Select the hard drive in the left pane of the opened window

(You should see the hard drive with the name of its manufacturer, if not changed earlier)

  • Now, go to the Partition tab in the right pane and
  • Click the target partition in the graphical view

(You should see the graphical view of the hard drive under Volume Scheme area.)

  • Drag this volume from its boundary to modify its size
  • Drag upward to trim and downward to enlarge.

(You should see three gray lines at the bottom-right corner of the selected partition. Click and hold these lines to drag.)

You can see the rapid change in the size of the selected volume under Partition Information area.

  • Click Apply to save the changes done so far.

Note: – In the bottom pane, you should see a property, i.e. Partition Map Scheme of the hard drive. You can modify the size of a Mac volume only if it uses GUID Partition Table.

(It is not possible to modifying any existing Mac volume if the Partition Map Scheme used is either Master Boot Record or Apple Partition Map.)

Moreover, if you find yourself unable to do such modifications, it would be better to ask for the help from professionals.

Guest article written by: Jyoti Kumari is a Mac user and believes in making life better with latest and useful technology in Mac.

[tp lang=”en” only=”y”]


[tp not_in=”en”]


9 thoughts on “Modifying Size of a Mac Partition without Data Loss”

  1. Thanks for this! I’ve tried several times to make partitions on my mac and I’ve had lost a lot of data! So thanks!

  2. is this utility easy to use and not consuming much resource

    it will be good if it easy to use like wondershare disk manager

    i will try it


  3. Hi Jyoti, thanks for the simple steps for modifying the size of a Mac partition. Usually we loss data in this process. Thanks for sharing the info.

  4. Hey Jyoti,

    I don’t have any mac devices and I also prefer to use windows OS than mac but that doesn’t mean I’m not interested in Mac. This post of your’s is indeed informative and helpful. I’ll keep this post in mind because we never know what would happen in the future. I might get a mac device for future usage. Thanks for this post.

  5. Thanks for sharing this useful information. Most users are nervous about doing disk partitions but this article shows how easily it can be accomplished under OS X.

  6. Hi Jyoti,i really agree with you thanks for the easy steps for modifying the size of a Mac partition. Usually we loss data in this process. you done good job Thanks for sharing the info.

  7. Finally i found something useful regarding my MAC partition. Till now i have tried couple of times and every time i lost my data. But i followed this article and safely divided my hard drive in to 3 parts without loosing single byte of my data.
    Thanks a lot


Leave a Comment

%d bloggers like this: