Free of charge.
I have the book on which this is based, and it's very useful.
Use this app to find and compare the carbon footprints of different items, activities, life events and foods. This app is designed for people who want to love their lives and for whom that now entails having some carbon awareness alongside everything else that matters to them.
Have installed it on my Nexus tablet, but it's not working for me at the moment... will try again later..