Calculator FAQs

FAQs for Carbon Footprint Calculators

The online carbon footprint calculation tools enable you to calculate your own carbon footprint.

Methodology

The online calculators on this web site follow the methodology outlined in DEFRA's Voluntary Reporting Guidelines, and uses the most up to date emission factors. The only exceptions to this are some country specific factors (which are sourced for international sources such as the World Resource Institute’s Greenhouse Gas protocol), and the Secondary Footprint calculations (which are based on estimates developed by Carbon Footprint Ltd).

The calculator uses emissions factors which take account of all greenhouse gases (i.e. CO2, N2O, methane etc.) released by the activities, with the results presented in units of metric tonnes of CO2 equivalent. In most cases that means the results will be slightly higher than if calculating CO2 only.

To include all aspects of your domestic footprint you will need to enter information about your home, personal travel and lifestyle over the last 12 months (or time period of your choice).

The following sections below give further information on how to use the calculator and answers to frequently asked questions.

Welcome Tab

Why do we need to select the country where I live?

This enables a more accurate calculation of your emissions from electricity usage, as the factor depends on how the electricity is generated in the region (e.g. from Coal, Gas, Nuclear, Renewables etc.).

The country selection also allows you to compare your results with the average for your country. Country averages in the Results Tab were sourced from the US Environmental Protection Agency (EPA).

What consumption period should I use?

Carbon footprint calculations are typically based on annual emissions from the previous 12 months, however you are able to select a more suitable time period (e.g. a month) if you so desire.

House Tab

What number do I put into number per household to calculate an individual’s Carbon footprint?

Select the actual number of people occupying the household in order to calculate your own personal proportion of the total household carbon footprint. Your individual footprint is calculated by dividing the total amount of energy by the number of people in your house.

If you want to calculate the full household’s footprint, then select 1 in the section.

Flight Tab

How are the flight emissions calculated?

Firstly the distances are calculated between the airports selected, using the greater circle method. This is then multipled by the DEFRA suggested factor, to take account of indirect distances, and then by the emissions factor specific to the type of flight (UK domestic, short haul or long haul) and the class of seat taken (e.g economy class, business class etc.).

What is the difference between selecting First Class and Economy seating?

Different emission factors were calculated according to the relative area on the aircraft occupied by different seating classes, for example a first class seat would occupy a larger area compared to an economy class equivalent per passenger and therefore attribute to a larger percentage of the overall planes emission.

How do you account for a plane being only partly full?

The emission factors assume an average occupancy of the plane, and for the emissions to be divided between the occupants in various seat classes.

What is the Radiative Forcing Factor?

Emissions from planes at high altitudes impact climate change more than if the emissions were released at ground level. To take account of this you have the option to factor up the emissions released by aviation Radiative Forcing Factor of 1.9. This is the factor recommended by DEFRA.

Car/Motorbike Tabs

What is the most accurate calculation method?

The carbon footprint from car usage can be calculated using different methods, providing the result in differing levels of accuracy. The combinations are listed in priority order with those at the top providing the most accurate results:

1. Type of fuel and the amount of fuel used per annum.

2. Type of Fuel, Annual Mileage and MPG.

3. Annual Mileage and CO2 g/km.

4. Make, Model, Fuel Type and Annual Business Mileage.

Do I enter the distance I drive in a week, or the total mileage / km shown on my car?

If you are calculating your carbon footprint for a 1 year period then enter the distance driven in the last 12 months. If you have selected a different period on the “Welcome tab” then enter the distance driven in time period selected.

Bus/Rail Tab

Where are the factors for bus and rail taken from?

The factors used for buses and rail were calculated based on publically available data from the major service operations, national statistics and the department for transport.

I only have stations and not distances?

The scope of the calculator only allows distances to be entered therefore please estimate the journeys between stations. One way to do this would be to use a web site such a Google maps to calculate the road mileage between the 2 stations.

Secondary Footprint Tab

What is a secondary footprint?

This is a measure of the emissions caused through the manufacture, delivery and disposal of products and services we buy. Most carbon footprint calculators ignore this part of your footprint, but without it you would risk under estimating your total footprint quite considerably.

What affect does buying organic have?

Organic food generally has a lower carbon footprint, compared to a food item grown in the same area. This is because it doesn’t have the greenhouse gas emission related to fertilizers and pesticides.

What is the difference if you eat meat or not?

Eating a lot of meat, especially beef, results in a higher carbon footprint than eating non meat products. Reducing your meat consumption, or switching to a meat with a smaller footprint, like chicken, will help to reduce your carbon footprint.

What factors are used to calculate my secondary footprint?

The secondary footprint is an estimate provided by Carbon Footprint Ltd to illustrate how the choices you make will indirectly impact the amount of carbon dioxide being emitted into the atmosphere. This figure should be used for guidance only. A detailed calculation of your secondary/indirect emissions is beyond the scope of this online calculator.

Haven’t the car emissions already been accounted for under the Car tab?

The emissions caused by the fuel used in driving the car are accounted for under the car tab section of the calculator. However, the emissions caused through the manufacture and servicing of your cars were not accounted for, so an average annualized amount of 1 tCO2 per car per year is added in this section.

Why do financial services account for so much?

The figure used is just an estimate of your share of the amount of emissions caused through the financial services industry. If you use financial services such as Banks, Insurance and Pension Policies, you will need to account for these services within your own secondary footprint