From the Unix prompt, typing the following:
du -s /home/youruser
This will give you a report back of the number of kilobytes (k) all files in your www directory add up to. You can also use -h switch like this to see human readable number in size:
du -sh /home/youruser
If you want to see the size of each folder under the current directory:
du -ah –max-depth=1
For example to check the usage of each folder in public_html:
cd ~/public_html
du -ah –max-depth=1