How to measure the carbon footprint ?

After I measured my footprint I found that I need four planets to live because my footprint was 3.97. I found my percentage of food was 18% and I think this percentage it's not correct because I don’t eat organic food. Also I found 41% for travel and this is a big percentage because I have a big car. The percentage of my house it's also high because there are too many people living in it. Finally h found my percentage of stuff was 18%. I think 3.97 it's very high so I need to reduce that number and in same time reduce carbon footprint.