Guide to Online Carbon Emissions Calculators

Have you ever wondered how sustainable your lifestyle is? There are many approaches to measuring the emissions footprint of a specific activity, such as a flight, or the general emissions generated by an organization or household. The level of detail that an emissions calculator requires directly correlates with the accuracy of the resulting estimate, resulting in a trade-off between accuracy and ease-of-use for websites that seek to simplify the user experience.

We reviewed online emissions calculators by calculating the annual carbon footprint of a sample household and the emissions of a roundtrip flight from Seattle to Austin. Some websites include online calculators for all activity types, while others focus on one sector or industry.

Types of Calculators

Household – Calculators for individuals and households typically measure the housing type and size, cost of heating and source used, food consumption habits, ground transport, and material goods.

Flights – A flight’s emissions are determined not only by the total miles flown, but also by the model of aircraft flown, the seating level (e.g. Economy versus First Class), and number of layovers.

Small Organization – There are comparatively fewer calculators for small businesses and organizations due to the increased complexity of these calculations, so most websites instead offer custom solutions for calculating carbon emissions. Of the available options, some choose to focus only on commercial electricity usage, while others account for vehicle fleets, business travel, and other emissions sources.


Carbon Footprint

This very comprehensive calculator for individuals, small businesses and flights allows users to save and download a report of their findings. This calculator can measure emissions by activity or sector (such as just transport or housing) or add them up for total emissions sum. Carbon Footprint also offers free calculators that can be installed on other sites. However, the calculator’s extensiveness might be a drawback for users wanting to get an estimate quickly.

Carbon Trust

This website includes tools for calculating specific aspects of business emissions (such as lighting or transport fleets) and for estimating the offset savings that a technology or policy upgrade could generate. The calculator is designed for business in Britain, so the assessments and suggested improvements might not be relevant to organizations outside the country.

EPA Carbon Footprint Calculator

This comprehensive calculator encourages proactive, planned actions in addition to offsetting current activities. Users can measure the positive impact of energy usage reductions (such as upgrading lightbulbs) on annual household carbon emissions. However, the EPA’s tool is not suitable for small businesses and does not include an emissions calculator for air travel.

The Guardian Carbon Calculator

Despite focusing only on air travel, this calculator only measures travel from the 100 most-traveled airports, so users might have to approximate their emissions by finding the closest airports to their destination cities.

ICAO Carbon Emissions Calculator

Simple to use, this tool from the United Nations’ International Civil Aviation Organization also includes their basic methodology to provide greater transparency. The calculated emissions were significantly lower compared to other flight calculators, which raised concerns about the tool’s accuracy.


The simple, user-friendly design makes this calculator one of the easiest to use and includes their calculations protocol, which also accounts for other emissions including nitrogen compounds. They also have offset calculators for cruises, organizations, events and cars. However, the limited factors used to calculate emissions for each activity risk being overly simplified, which makes getting an accurate emissions estimate more difficult.

Nature Conservancy

This tool focuses on helping users compare their carbon footprint to that of other households. The user experience is difficult to navigate because the calculator tools do not have clear instructions and do not ask for the number of people living in a household. The offset calculations seemed very high compared to those of other calculators, which possibly results from the lack of comprehensive details.

United Airlines and Conservation International

This emissions calculator is designed specifically for United Airlines but does not include all airports in the dropdown menu, so estimates might have to be made for a roundtrip flight to the nearest destination city instead. This was the only online calculator in this review to also list the fuel efficiency of the aircraft used on a flight.

World Land Trust

This easy-to-navigate calculator beaks down emissions into different categories. The household emissions calculator, however, only accounts for electricity and does not provide a more detailed usage breakdown.


The slick user experience is a compelling way to visualize household emissions and also provides comparative statistics about global average energy consumption to help illustrate the sustainability (or lack thereof) of your lifestyle. The calculator asks very generalized questions, and there is no way for users to download their data for reference. Some questions are also UK-specific.