While QDirStat is a wonderful GUI tool for reviewing a drive's use of space, ncdu provides a similar thing in a textual context. This is particularly useful in a headless system setup, where there is no GUI; such as may be found on a server. In that type of situation, the terminal is your best friend; and that's where ncdu will work wonders.
But that's not to say that you will not jump to ncdu first even on your desktop ... the speed that ncdu runs at and its ease of use will make you remember it.
Like QDirStat, you can feed ncdu a folder to start with, when you first run it.

You can use the left and right arrow keys to move back and forth through previous folders and [enter] to drill down into a folder. And, you can delete highlighted files by pressing 'D'.