du

$ du -c
This gives you a grand total as the last line of the output. eg. 
[root@mx2 MailScanner]# du -ch
... .....
116K    ./reports/cz
116K    ./reports/cy+en
1.8M    ./reports
16K    ./mcp
8.0K    ./conf.d
2.3M    .
2.3M    total

 $du -sh
Gives you directory size  eg. MailScanner is directory
[root@mx2 etc]# du -sh MailScanner
2.3M    MailScanner

[root@mx2 ~]# du -sh *
4.0K    Mail
5.9M    MailScanner-4.84.6-1
5.7M    MailScanner-4.84.6-1.rpm.tar.gz
3.3M    rpmbuild
412K    sent
100K    stuff
22M    webmin-1.680-1.noarch.rpm