How to check your Mac's free hard drive space
In recent versions of OS X, you can easily check your disk usage from the About box. Pop open the Apple menu, then select About This Mac. On OS X Yosemite or newer, click the Storage tab in the toolbar to see how much disk space you have available. (On OS X Mountain Lion or Mavericks, click the More info... button, then click Storage.) You’ll also get a simplified overview of what sort of files are eating up your storage space.
You can also view your free disk space from your Mac’s Disk Utility app. Open Spotlight by clicking the magnifying glass in the upper-right corner of the screen, then type Disk Utility in the search box that appears. Once Disk Utility comes up in the list and is highlighted, press the Enter key.
Once Disk Utility opens, select your hard drive’s name from the list. I renamed my hard drive “Sad Pandacat,” but if you didn’t change its name, it’ll be named “Macintosh HD.” Look in the lower-right corner to find your drive’s capacity, its available space, its used space, and the number of files on the drive. You can also check the free space for any drive you have connected to your Mac from this window, be it a USB flash drive or external hard drive.
The Finder gives you at least a couple ways to see how much free disk space you have. The first method is to check the Get Info window for your hard drive.
First, you need to find your hard drive in the Finder and select it. If it appears in the Finder window sidebar or on the Desktop (it doesn’t by default—go to Finder > Preferences... to change that), click your hard drive’s icon in either of those spots. If your hard drive icon doesn’t appear there, go to Go > Computer, then click the hard drive icon. Pop open the File menu, and select Get Info, and note the drive’s capacity, available space, and used space.
If you would like to have an overview of your free disk space at all times from the Finder, you can turn on the Finder’s status bar. Open a Finder window if you don’t have one open already (click the Finder’s Dock icon or go to File > New Finder Window).
Next, open the View menu and select Show status bar: This will show you how many items are in the current folder, and if you’re viewing a folder on your hard drive (such as your Applications or Documents folder), you’ll also get a readout of your hard drive’s free space.
This method works fine if you know your way around your Mac’s file structure reasonably well, but Apple has worked to hide a lot of the file system by default in recent years, so if you don’t have a sense of place on your Mac, the first two options are better ways to go.