Well, that depends how you live, Doug. If you live like a Londoner, Herbert Girardet says three planets, but if you live like an American, I suppose that might mean a bit more. Myself, I think that the calculation is fallacious, since he only considers human outputs as waste, not as positive inputs. (see my exchange with Girardet in Rising East ( http://www.uel.ac.uk/risingeast/archive03/academic/heartfield.htm and http://www.uel.ac.uk/risingeast/currentissue/feedback/girardet.htm ). Furthermore, the calculation "proves" that human existence is impossible today, which seems a bit far-fetched to me.
However, there is an underlying point here, and that is that nobody is forcing anyone to consume the planet. In his recent book and accompanying website George Monbiot argues that environmentalists who fly are hypocrites. Each flight equals all of your carbon ration for the year. The argument seems unassailable to me: If you believe that anthropogenic climate change will lead to global catastrophe, then you should not fly.
Ever since he put the gauntlet down, the newspapers here have been checking over the records to show that our leading environmentalists are also very frequent fliers. Indeed I found records that Monbiot himself flew to South Africa and Australia in recent years ('A green snag they omitted to mention', Sunday Times, 1 October 2006, and see my review http://www.spiked-online.com/index.php?/site/article/1839/ ).