You can make different pledges and it will recalculate your carbon footprint automatically. It also offers lots of information to reduce your footprint as low as possible. But only up to 20/month. What sucks is that I'm already doing a lot of these things, but they don't have an option to just say "already doing it".
Mine is 245 with a carbon output of 9.3 right now. It will go down as soon as I can confirm some of my pledges for things I've been doing for years. It also compares your usage to your city, state, etc. So mine looks like this:
MY SCORE 245 9.3It helps me see how far I've come (comparatively speaking) and how far I still have to go. The cool thing is that it provides information to help you get even better numbers.
MY CITY 362 16.3
TEXAS* 381 17.2
UNITED STATES 351 15.1
WORLD 335 13.9