How does your calculator work?

Once you have entered data into the calculator, we multiply it by emissions factors. For example, if you input that you have driven a certain number of miles in a large petrol car, we multiply that distance by a factor showing the greenhouse gases released for each mile.

The emissions included are the three major greenhouse gases: carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O).

The emissions factors we use and the methodology behind the calculator follow the UK government's guidelines for calculating a carbon footprint.

For flights, there is currently uncertainty over the other non-CO2 climate change effects of aviation (including water vapour, contrails and NOx emissions), and hence the impact of these effects has not been included. Our international flight calculations assume travel in economy class.

If you have used a calculator on another website, you can offset the footprint that it came up with by entering it into our website.