Apple Hardware Disk Utility Unallocated Space on my Hard Drive While trying to get Boot Camp set up on my MacBook Pro 15 inch Retina 2015 it asked me to partition my hard drive. Doing so I partitioned my 1 TB hard drive so that it dedicated 750 gb to mac and 250 gb to Boot Camp. However the Boot Camp set up was not successful and now my Mac's hard drive is only 750 GB big. With Boot Camp uninstalled it is still 750 GB. The 250 GB can not be added again on my Mac. Every time I try and add a partition to the "unallocated space" it does not work. I can't get my hard drive back to the full 1 tb. It looks something like this. 

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Someone please help me restore my Mac to its 1 TB hard drive. It would be very much appreciated.
OS X Yosemite automatically converts hard drives to Core Storage volumes, whose sizes can't be changed. You need to undo the Core Storage conversion.

Here are instructions for making that happen. (source - this method worked for me). This method should be non-destructive, but as always, take a backup first! 


Boot into Recovery HD. If for any reason you don't have Recovery HD, then you'll have to make a bootable Yosemite drive and boot into that.
In the Menu Bar, select Utilities > Terminal.
Run diskutil cs list. You'll get an output that looks like this (credits to the Ask Different user in my source):





Select your Logical Volume ID (the one highlighted in the screenshot) and copy it to the clipboard.
Run the Terminal command diskutil cs revert Paste-Your-Logical-Volume-ID-Here.
Run diskutil cs list to verify that your computer can't find any CS volumes.
You're done! Now Disk Utility should be able to resize your HD!