Carbon footprints represent the effect of human activities on the climate in terms of the quantity of greenhouse gases generated through individual lifestyle choices.

Web based carbon footprint calculators typically focus questions upon energy and transportation related carbon dioxide (CO2) emissions. The output is an overall figure for a given individual in units of carbon dioxide produced per year (usually kilograms) - their carbon footprint.

Such calculations provide an indication of the climatic impact of specific aspects of individual lifestyles and help to identify those areas where more sustainable choices could be made.