There are several ways to measaure your environmental footprint.
Ecological footprinting measures the impact of a person or community on the planet, in terms of the amount of land required to sustain their use of natural resources. See www.footprintnetwork.org.
Carbon footprinting measures the total amount of greenhouse gases (Carbon dioxide, methane, etc...) produced, directly and indirectly, by human activities. It is usually expressed in equivalent tonnes of carbon dioxide (CO2e)
WWF's footprint calculator presents your footprint as a % of the UK's 2020 carbon target.
or you can calculate your ecological footprint using http://www.footprintcalculator.org/.
Have a go!