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Explaining the terminology in our carbon calculator

We've tried to keep our carbon calculator simple, so you can quickly start making changes to your lifestyle and do your bit to tackle the climate crisis. Calculating and offsetting carbon emissions is a complex topic, and from time to time we can't avoid using technical terms. We've explained the ones used most often below.

Carbon footprint

This is shorthand for someone's impact on the planet. Almost everything we do releases greenhouse gases into the atmosphere, from how often we fly, to the type of shampoo we use. The result of all these actions combined is your carbon footprint, measured in tonnes of carbon dioxide equivalent, or CO2e.

Carbon offsetting

Carbon offsetting is a way to compensate for your carbon footprint by funding carbon reduction projects in other parts of the world. So, for every tonne of CO2e produced by your lifestyle, you can fund offset projects to reduce the amount of CO2e in the atmosphere by a tonne. Common carbon reduction projects include protecting forests, developing clean energy sources or more efficient energy products. When every possible action has been taken to reduce their carbon footprint, individuals and organisations can offset their remaining emissions to become 'carbon neutral'.


CO2 is shorthand for carbon dioxide. It's one of the seven major greenhouse gases that contribute to climate change. Carbon dioxide exists naturally in earth's atmosphere, but human activities since the industrial revolution have increased the amount of carbon dioxide in our atmosphere to unsafe levels. More carbon dioxide in the atmosphere traps more heat that would otherwise be able escape into space. This has warmed our planet, causing climate change.


CO2e is short for carbon dioxide equivalent. This covers all greenhouse gas emissions that contribute to climate change, including carbon dioxide (CO2), methane (CH4), nitrous oxide (N20), and refrigerant gases like hydrofluorocarbons (HFCs).

Some of these cause more global warming than others. Using CO2e makes it easy to compare the impact of activities that emit different greenhouse gases.

For example: 1kg CH4 = 25kg CO2e. This tells us that methane is 25 times more powerful as a greenhouse gas than carbon dioxide (CO2).

Consumption footprint

This takes into account things you buy, or services you use, that cause emissions outside the UK. It's important to include the carbon emissions we cause beyond our borders, because about 20% of our emissions come from outside the UK. This is caused by importing goods made elsewhere, for example steel.

The average consumption footprint of the average person living in the UK is currently 13 tonnes CO2e per year.

Emissions factor

An emissions factor tells you how much CO2e is created per unit of activity. You can't estimate a carbon footprint without them. For example, the emissions factor of taking the train is 0.0662kg of CO2e per mile. Multiplying that by how many miles you travelled will give you the carbon footprint of that journey.

Life cycle emissions

Life cycle analysis is a way of looking at the environmental impact of a product or activity throughout its entire life. For example, to estimate the carbon footprint of a laptop, you’d need to consider the extraction and processing of raw materials, the manufacturing, transport, use and end of life. We use life cycle emissions for the different products you buy or the food you eat in the carbon calculator.

Net Zero

In June 2019 the UK government committed to a target of Net Zero emissions by 2050. That means reducing the UK's emissions by 100% from 1990 levels. But there will always be emissions that can't be reduced. To reach Net Zero, these unavoidable emissions must be matched by removing emissions in the atmosphere by the equivalent amount.

Production footprint

A 'production' footprint is a way of measuring a carbon footprint that doesn't take into account the emissions produced outside of the UK thanks to a person's lifestyle. The average person's production footprint in the UK is 8 tonnes CO2e per year.

Your "target"

There's no consensus on what an individual's Net Zero target should be. So we've followed the Committee on Climate Change (CCC)'s recommendation of about 1 tonne CO2e per person, which assumes everyone in the world has a fair share of emissions.

In the same way the UK can't reach zero emissions, it's not possible for a person to have no carbon footprint. This is because we all still eat, travel, and do other everyday activities. 

Our carbon calculator works out your carbon footprint before you've offset any of your emissions. To make it a fair comparison, the Net Zero target also shows what your carbon footprint should be in 2050 before you've offset your unavoidable emissions. Once you've done that, your footprint will effectively be zero.