Instructions
Turn on the PlayStation 3 console and the PlayStation 3 controller.
Select the profile you wish to sign in with and press "X" on your controller. After signing in, flick the analog stick left to "Settings."
Move down and click "System Settings" at the bottom of the "Settings" menu. Click "System Information," which is just above "About PlayStation 3."
Look at "Free Space." You will see "XX/ZZ" where "XX" is the amount of free space you have available, and "ZZ" is your PlayStation 3's total hard drive capacity.