About

A carbon footprint is the total amount of greenhouse gas emissions (mainly carbon dioxide, methane, nitrous oxide, water vapor and ozone) that is produced directly and indirectly by a person, an organisation, an event or a product.

Direct emissions, also called primary footprint, come from sources directly controlled by the person(s) or activity in question, for example heating one's house. Indirect emissions or secondary footprint are emissions that are the consequence of a person(s) actions using sources owned or controlled by someone else, for example fuel that was used to transport the products you buy from the factory to the store.

The global average carbon footprint is approximately 4 tons of CO2-equivalent per person per year [source]

Note the difference with ecological-footprint that measures the total impact (so not only greenhouse gas emissions) of a person, organisation or activity on the Earth's ecosystems.

Online carbon footprint calculators:

Personal/Household

• Carbonfootprint.com
• Berkeley University - CoolClimate Carbon Footprint Calculator
• Conservation International for US residents
• EPA USA - Household Carbon Footprint Calculator for US residents
• Nature Conservancy for US residents
• Terrapass for US residents, calculate for individuals, business or events
• KnowYourCarbonFootprint.com for US residents
• WWF UK Footprint Calculator for UK residents

Kids

• Meet the Greens - Zero footprint youth calculator temporarily broken?

Business

• Greenhouse Gas Protocols Excel worksheets for many specific purposes
• Carbonfootprint.com registration required
• Terrapass for US companies, requires registration)

Transportation

• Eco Passenger compares train, car and flight for Europeana destinations
• ICAO calculator for air travel, includes aircraft type information and route specific data
• MyClimate.org in English, German or French

History

The idea of a "carbon footprint" was popularized by fossil fuel company BP in 2005.