How much space a directory occupies on your hard disk?

In order to find out exactly how much space is occupied by /var.

deby:~# du -hs /var
105M    /var

You might need to know spread space below /var.

deby:~# du -h --max-depth=1 /var
4.0K    /var/lock
...
4.0K    /var/opt
80K     /var/run
105M    /var