If you’ve changed the size of a partition, you may be able to fix it without erasing the entire drive.

Apple made it simpler to resize partitions-logical divisions of a disk drive into individual mountable volumes with different properties-several releases of macOS ago. A Macworld reader resized their main quantity to 369GB to create a TRAINING partition, but realized it had been too small then. They wondered how exactly to fix this.

In the proper circumstance, you can merely follow these actions without needing to back up the whole drive, reformat and erase it, and add new partitions.

Always back again up your drive before trying to resize partitions in the event something goes incorrect, or you click to proceed on a destructive operation accidentally.

Launch Disk Utility.
Choose the disk, not the quantity, in the left-hands lists of disks.
Click on the Partitions button.
Now you can delete other partitions (select and click on the - button), and enter the brand new size of your primary partition in its Size field.
Warning! Click to proceed Apply, and Disk Utility will warn you whether it shall be a destructive operation, deleting the partition’s re-creating and data, or not. If it’s non-destructive, proceed.
I haven’t discovered a complete consistency where drives have nondestructive resizable partitions or not really. You can read a complete lot of fine detail about macOS drive partitioning, and still find a volume that fulfills all of the parameters for resizing without erasing, but still find out by Disk Utility that the partition will be erased.