Is it possible to use ls in Unix to list the total size of a sub-directory and all its contents as opposed to the usual 4K that (I assume) is just the directory file itself?

total 12K
drwxrwxr-x  6 *** *** 4.0K 2009-06-19 10:10 branches
drwxrwxr-x 13 *** *** 4.0K 2009-06-19 10:52 tags
drwxrwxr-x 16 *** *** 4.0K 2009-06-19 10:02 trunk

After scouring the man pages I'm coming up empty.