What is a carbon footprint - definition

A carbon footprint is defined as:

The total amount of greenhouse gases produced to directly and indirectly support human activities, usually expressed in equivalent tons of carbon dioxide (CO2).

In other words: When you drive a car, the engine burns fuel which creates a certain amount of CO2, depending on its fuel consumption and the driving distance. (CO2 is the chemical symbol for carbon dioxide). When you heat your house with oil, gas or coal, then you also generate CO2. Even if you heat your house with electricity, the generation of the electrical power may also have emitted a certain amount of CO2. When you buy food and goods, the production of the food and goods also emitted some quantities of CO2.

Your carbon footprint is the sum of all emissions of CO2 (carbon dioxide), which were induced by your activities in a given time frame. Usually a carbon footprint is calculated for the time period of a year.

The best way is to calculate the carbon dioxide emissions based on the fuel consumption. In the next step you can add the CO2 emission to your carbon footprint. Below is a table for the most common used fuels:


  • For each (UK-) gallon of petrol fuel consumed, 10.4 kg carbon dioxide (CO2) is emitted.
  • For each (US-) gallon of gasoline fuel consumed, 8.7 kg carbon dioxide (CO2) is emitted.
  • If your car consumes 7.5 liter diesel per 100 km, then a drive of 300 km distance consumes 3 x 7.5 = 22.5 liter diesel, which adds 22.5 x 2.7 kg = 60.75 kg CO2 to your personal carbon footprint.
fuel type unit
CO2 emitted per unit
Petrol 1 gallon (UK)
10.4 kg
1 liter
2.3 kg
Gasoline  1 gallon (USA)
8.7 kg
Gasoline  1 liter
2.3 kg
Diesel 1 gallon (UK)
12.2 kg
Diesel  1 gallon (USA)
9.95 kg 
1 liter
2.7 kg
Oil (heating)
1 gallon (UK)
13.6 kg
Oil (heating)  1 gallon (USA)
11.26 kg 
Oil (heating)
1 liter 3 kg

Each of the following activities add 1 kg of CO2 to your personal carbon footprint:

  • Travel by public transportation (train or bus) a distance of 10 to 12 km (6.5 to 7 miles)
  • Drive with your car a distance of 6 km or 3.75 miles (assuming 7.3 litres petrol per 100 km or 39 mpg)
  • Fly with a plane a distance of 2.2 km or 1.375 miles.
  • Operate your computer for 32 hours (60 Watt consumption assumed)
  • Production of 5 plastic bags
  • Production of 2 plastic bottles
  • Production of 1/3 of an American cheeseburger (yes, the production of each cheeseburger emits 3.1 kg of CO2!)

To calculate the above contributions to the carbon footprint, the current UK mix for electricity and trains was taken into account.

Carbon dioxide is a so called greenhouse gas causing global warming . Other greenhouse gases which might be emitted as a result of your activities are e.g. methane and ozone. These greenhouse gases are normally also taken into account for the carbon footprint. They are converted into the amount of CO2 that would cause the same effects on global warming (this is called equivalent CO2 amount).

Few people express their carbon footprint in kg carbon rather than kg carbon dioxide. You can always convert kg carbon dioxide in kg carbon by multiplying with a factor 0.27 (1'000 kg CO2 equals 270 kg carbon). See my comment to the article about personal responsibility for global warming .

The carbon footprint is a very powerful tool to understand the impact of personal behaviour on global warming. Most people are shocked when they see the amount of CO2 their activities create! If you personally want to contribute to stop global warming, the calculation and constant monitoring of your personal carbon footprint is essential.

For registered users, there is a carbon footprint calculator on this website, which allows to store individual activities like, e.g. travelling by car, train, bus or air plane, fuel consumptions, electricity bills and so on (we call the individual contributions "carbon stamps"). You can then see the amount of CO2 created for each individual activity. You can do this either in advance and use it as a help for decisions or afterwards to continually sum up your carbon dioxide emissions. Klick here to see a sample carbon footprint with some activities.

An off-line carbon footprint and primary energy consumption calculator (Excel sheet) is already available in the download section.

There are graphs available on this site for the CO2 emissions per capita by country (average carbon footprint by country). In the medium- and long term, the carbon footprint must be reduced to less than 2'000 kg CO2 per year and per person. This is the maximum allowance for a sustainable living .