Getting size of mailboxes or accounts.

Hi all. Another Mail question. How do I get the size of email on my mac? Google says control clicking on an account, I can't seem to do that. My local mail in ~library/mail is 4.31 GB, so that's something, but I've got a couple IMAP accounts I'd like to know the size of too. I assume the stuff in ~/library/mail is local stuff imported from Thunderbird on Windows, and those IMAP accounts are separate.