Grammatical English has about a bit of entropy per character (Wikipedia has it between 0.6 and 1.3). Most passwords won't be fully grammatical, or even close, but it's a decent worst-case bound for passwords chosen by English speakers to be memorable. If you have a specific scheme it obviously goes out the window.

with all the password leaks I wonder if you could determine the likely scheme used by a given user by the leaks associated with their email address.