A carbon footprint measures the total greenhouse gases produced by a person, product, company, or activity. It is usually expressed in tons of carbon dioxide equivalent. That unit bundles different gases, like methane and nitrous oxide, into a single number based on their warming power.

The concept helps make emissions visible. A flight from London to New York adds roughly a ton of CO2 per passenger. A beef burger carries a heavier footprint than a bean burger. A data center's footprint depends on its power source. These comparisons are rough, but they guide choices.

Footprints are hard to measure precisely. Supply chains stretch across continents. Data is incomplete. Companies often calculate their own numbers, which invites greenwashing. Third-party verification helps. So does focusing on the biggest sources first: electricity, transport, heating, and food. Small changes matter less than structural ones.

Main components

• Direct emissions from fuel use
• Electricity and heating
• Transport and travel
• Food and agriculture
• Goods and services