How to Partition a Hard Drive on Mac OS X

by John Ford

The partitioning of a hard drive on a Mac OS X computer offers you the ability to have multiple spaces for backing up your computer files along with the flexibility of running different operating systems such as Windows, Linux and even other instillation's of the Mac OS. Keep reading to learn how to partition your Mac OS X hard drive.

Disk Utility is Located in the Utilities Folder

In an open Finder window, click on "Applications" in the Finder window Sidebar. Cursor down the "Applications" listing to the "Utilities" folder. Find the "Disk Utilities" application in the "Utilities" folder and double-click the application to open it.

Selecting a USB Thumb Drive for Disk Partitioning

With the "Disk Utility" application launched, select the disk you wish to partition from the available disks connected to your Mac in the left-hand window. Now select the "Partition" radio button at the top of the "Disk Utility" application window to access the partition preferences.

A USB Thumb Drive with 3 Partitions selected.

Select the pop-up button, just under the "Volume Scheme" preferences in "Disk Utility," and select the number of partitions for your disk. Hold the mouse down and drag to select the number of partitions. The partitions will automatically represent an equal amount of divided disk space. For example: If you have a 30 gigabyte drive, selecting 3 partitions will divide the disk into 3 10 gigabyte partitions.

Adjusting Partition Size in Disk Utility

Make adjustments to partition size by clicking and dragging on the "Re-size Bars" under and in between each partition of your hard disk, if you wish to create custom sized partitions.

Disk Utility Formatting Options for Partitions.

Click on the "Options" button just below the Volume Scheme window to select formatting options of your new partitions. Select "GUID Partition Table" if you are using the disk for an Intel based Mac, "Apple Partition Map" for a Power PC processor based Mac or "Master Boot Record" if you will be installing a Windows Operating System or sharing the disk with a Windows based computer. Click "OK" when finished.


Click the "Apply" radio button in the bottom right corner of the "Disk Utility" window. Then click the click the "OK" button in the pop-up warning window that appears on top of the "Disk Utility" window to re-format and partition your drive. Warning: Clicking the "OK" button will reformat your drive and erase all data from the disk.


  • close Warning: Clicking the "OK" button will reformat your drive and erase all data from the disk. Make sure you have backed up all data you wish to keep from the disk before partitioning and re-formatting any drive.

Items you will need

About the Author

John Ford is a Fort Lauderdale, FL native with a background in Broadcasting, Print & New Media. A Recognized expert in Broadcasting & Creative Services with stints at the ABC Radio Networks and as VP of New Media for Sabo Media. A respected writer for Parade Magazine & National Geographic. Webmaster, Apple Certified Support Professional and a published singer/songwriter

Photo Credits

  • photo_camera John Ford: Apple Computer