Here is what I do. I am sure there are other ways, but this works for me.
If I want to see the size of my /home/bruce directory, this is the command I would run:
du -sh /home/bruce (substitute with your own user)
The alternative is you could run that command from the directory of which you need this size:
Another alternative is if you want to see how subdirectories break down, just run
du -s /home/bruce
The last line of that result will be the total for all the directories.
Hope this helps,