Resize Partitions in Mac OS X with Disk Utility
You can easily resize any disk partition in Mac OS X using the included Disk Utility app, located in /Applications/Utilities, and you can even resize a mounted volume. In fact, you can grow or shrink HFS+ (Mac OS X) Partitions on the fly, with the resizing done live regardless of whether the drive is internal or an external drive, or even the boot volume.
A word of advice: Resizing mounted boot volumes isn’t always the best idea in the world because there’s a tiny potential something could go wrong. Before you go messing around and resizing your partitions, be sure to backup your data using Time Machine or whatever other backup service you prefer and make a recent back up.
Resizing a Mac Drive Partition with Disk Utility
- Open Disk Utility and select the hard drive with partitions you wish to resize
- Select the “Partition” tab and then click the partition to resize, then click and hold on the little dragging widget in the corner as shown in the image below
- Size the partition as you wish, then click “Apply” for the changes to take effect
Optionally, click the [+] icon if you need to add a partition, read more about that here
This has been possible from Mac OS X Leopard onward (and obviously Snow Leopard, Lion, and Mountain Lion). As mentioned earlier, it’s always a good idea to back up important data before making adjustments to partition schemes, Time Machine is by far the most efficient way to do so.
[ animated gif from CreativeTechs ]
I see that the article is almost a year old, but I have a question about this and hope you can still answer this.
My Mac HD is also formatted as Mac OS Extended (journaled), but won’t allow me to resize (enlarge) this partition. I haven’t got a ‘drag’ corner.
It says something about being my startup disc, which isn’t being mentioned in the article.
Is this what causes the problem?
Did you ever get an answer? I’ve got the same problem and haven’t found a solution yet. Thanks.
Disk Utility does not let you resize a partition that has a Master Boot Record (MBR). You can see at the bottom of the window in the information if that is the case for your partition. These type of partition are the ones that are used for booting a system.
No. MBR is never used as the partition scheme on any EFI system. GUID Partition Table is the type of scheme.
Yes thats right. Any application cannot be applied to resize the boot volume of the current system. It must be attached as an external hard drive to resize the boot volume. Well , a few days ago I have tried the Stellar Partition manager successfully.
Was looking for some partitioning information and stumbled across this posting. I tried out of curiosity and it works perfectly fine. If we have multiple partition on a disk (internal/external), we need to choose the main disk from the Disk Utility by clicking on the disk and not on the partition and select tab and it works beautifully. I did this on my boot volume (system partition) while running applications without any issue I could partition. But I see that this is not helpful for my situation as this doesn’t let one to grow the partition. i.e. say if one has 100 gb x 3 partitions, we can’t resize and increase the size like, say make one partion 50 gb and use the 50 gb to make the other partition 150gb. But you can free up 50gb and create a new partition to make it 2x50gb and 2x100gb.
Use first aid and it should remove the master boot record. It worked for me.
First Aid tab allows Verifying/Repairing a partition or Verifying /Repairing permissions for Mac OS. It has nothing to do with master boot record.
try to boot with recovery hd and then resize partitions
found out issue, if u want to transfer files instalations to another disk – if ur old disk is for example 500gb and u want to transfer to 256gb ssd it will say – not enought disk space even if ur 500gb disk is filled with 100gb info, u need to resize it first to a size your new disk have
Hi, I got a question as simply as it gets about Disk utility. Some time ago I did two partitions on my Hard Disk, One called Macintosh HD with 435,00 GB long and other One called Windows 7 with 203,00 GB long, it was planned to install Windows 7 on the second partition but i´d definitely not since I purchased a laptop with Windows 7 on it.
So now I want to delete the Windows 7 partition and enlarge the main partition so that I just have one partition of 638,00 GB long. the question is ¿the process of enlarge the main partition from 435,00 GB till 638,00 GB would end up on a lost of main partition data? Thank you very much in advance.
You can delete the Windows 7 partition without impacting the primary OS X partition with Disk Utility. Just remember to back up your Mac beforehand just in case something goes wrong, which there is always a chance of when editing file systems and partitions.
I know that, I do remark my question ¿the process of enlarge the main partition from 435,00 GB till 638,00 GB would end up on a lost of main partition data?
No loss of data on the Mac OS partition unless something goes really wrong (power failure, for example). Always keep a backup, even if you don’t plan to change anything about the partitions. You just plain need a backup. If you remove the Windows partition, you can add the available space to the Mac OS partition, and then “Apply”. Removing any partition removes all files on that partition. DUH! Sorry to say the obvious, but someone may need to know.
BTW, you must use Boot Camp to create any Windows partition on a Mac. Boot Camp creates a hybrid MBR partition on a GPT scheme drive.
works great
The issues arises when we decrease one partition and try to merge that free space into another one. It can’t be done with disk utility. I did the job with Stellar Partition manager, without any extra effort.
Huh? I have done this more than one on more than one Mac, so I strongly disagree. I’m pretty sure this is the topic of this article.
Has anyone run into issues with the new 3T drives? I followed all of these steps recently in order to split my drive up to where BootCamp could work with it (needs to be 2.2 TB or less). First of all, I started off trying to split the 3T into two 1.5 partitions. That should have left enough for Bootcamp to use disk0s4. Instead, Disk Utility gave me one 800G and one 2.2T partitions! AND, there was no option to resize. So, I followed Apple’s How to’s to resize the first partition (necessary, because 800G left me with only 90G free space!), which was to remove the second partition. I did, and now I can neither resize the old partition or add the second one back.