total size taken by directory

HI ALL,
i am a beginner in unix world.
can anyone please tell me the way to find total size taken by each directory (including size of all subdirectories and files) present under /var.
e.g what is space occupied by /var/adm , /var/admin etc.
its a simple question but still i dont know the answer.

try
df -k

I would do:
cd /var
du -sk * | sort -n