How to find total MB of a directory plus all subdirectories

Wed Mar 7 03:32:49 UTC 2007

On Tue, Mar 06, 2007 at 22:01:38 +0100,
  Nigel Henry <cave.dnb at tiscali.fr> wrote:
> This is a silly question perhaps. I have my soundfiles in a directory named 
> Sounds Library, this contains many subdirectories, which contain the .wav 
> files.
> 
> What command can I use to find out the disk space this directory is taking up, 
> including all the files that are in the subdirectories?

du -k