There are lots of different versions of this kind of environmental footprint calculator, but this one seems to cover the important bases really well.

Consumer Consequences – from American Public Media

I’m bummed that I require 4.3 planets to sustain everyone at my lifestyle, but more than half of that  is due to driving. In OKC with everything spread out, no public transportation, and no sidewalks in my part of the burbs driving is a fact of life that no one questions. Maybe someday.

Go check it out – how many earths do you need?