Carbon calculators

Last updated: Nov 2007


Carbon calculators are essential tools for the growing movement of voluntary carbon reduction, but they can also misrepresent the costs of climate change. Dan Welch investigates and recommends some of best.



In issue 100 we published a 'carbon calculator' developed by Quaker Green Action (QGA). Through pen and paper calculations readers can work out their carbon footprint, or the contribution to climate change made by different sectors of their lifestyle, from home heating to eating organic food. We invited readers to share their tips through our Low Carbon Lifestyles feature. 

Since then the language of "carbon reduction" and "low carbon diets" has hit the mainstream. Dozens of web-based carbon calculators have popped up, varying in sophistication and purpose. Quick, multiple choice questionnaires are useful for educational purposes. 

More complex calculators employ estimates, calculations in the strict sense, or both. These more complex types, such as QGA, enable the user to assess their position against per capita emissions (national total divided by population) rather than simply domestic emissions. More recently sophisticated 'carbon accounting' sites have begun to appear for the ongoing carbon counter to regularly update their figures. 

Non-direct emissions, or the "embedded" carbon of products and services, are the most difficult to estimate.

Despite experimental schemes in this area it is probably unrealistic that any degree of accuracy can be achieved. [1] However, estimates empower individuals by demonstrating how their consumption decisions and lifestyle choices impact emissions.


The case for voluntary carbon reduction

In his recent book "How to Live a Low Carbon Life," Chris Goodall makes a strong case that the only hope for systemic action on the part of government and business to cut emissions is for individuals to lead the way with voluntary reduction. Politicians, he argues, will only advocate serious reduction measures when they are convinced a constituency exists supporting those measures; business will only respond when there is a big enough market.

Per capita UK emissions of greenhouse gasses are equivalent to about 12.5 tonnes of carbon dioxide[2]. Individuals are responsible for a little under half of these, or 6 tonnes, through energy use in the home and for transport.


Analysis of the typical carbon footprint points towards the key role of voluntary action.

Even with the political will and Herculean effort, converting the power generation system to renewable energy would take decades. As for transport, there is simply no non-fossil fuel alternative that would maintain current levels of mobility in the foreseeable future. The supply side of the equation can't deliver the necessary reduction in emissions needed to mitigate climate change in the time required. We need radical reductions on the demand side.

If the entire UK electricity supply was switched to renewable energy overnight, it would only reduce domestic emissions for the average UK household on mains gas by about 12.5%. Average emissions from car and air travel, however, are around three tonnes of CO2, or half of individual emissions.


Reducing personal carbon emissions can also be seen as a matter of individual self interest.

The International Energy Agency, the industrialised countries' energy watchdog, warned in July this year that the world is facing an oil supply "crunch" within five years[3], heralding a probable crisis of supply and rising energy prices.

With such a prospect on the horizon, taking step-by-step progress towards low carbon living could be seen as prudent insurance.


Education or misrepresentation?

Some carbon calculators can be seriously misleading, nowhere more so than the aviation emissions calculators of some carbon offsetting companies. These calculations are complicated by the length of flight, type of aircraft, number of passengers, cargo - even whether economy or business.

But most importantly, planes also emit other greenhouse gases and their warming effect at high altitude is amplified, meaning CO2 figures must be multiplied to show the true effect. Most studies[4] put this multiplier between x 1.9 and x 4. The multiplier most often quoted from the International Panel on Climate Change (IPCC) is x 2.7. Many offset companies simply ignore the multiplier[5].

The government has proposed that there should be a standardisation of carbon calculation used by offset providers[6]. This would be a step forward, but, as the proposed code of best practice is voluntary, how this would work in practice is unclear.


A Government Calculator

In June 2007 the government launched its "Act on CO2" carbon calculator. It presents the user with a one-way journey, so any comparisons between lifestyle options is very difficult. It is designed to produce an Action Plan for the user rather than be used as a serious tool.

A surprising feature of this calculator is that when the option for a green electricity tariff is selected it makes no difference to emissions. The FAQs note "the low carbon factor of the green energy you are using has already been accounted for and helped to slightly lower the general CO2 intensity of our electricity supply." It is intriguing to find the government presenting its own renewable energy legislation as quite so disempowering to the consumer.

The QGA calculator also makes this assumption, while Mark Lynas' Carbon Calculator takes the overly optimistic view that any green tariff equals zero emissions. The most sophisticated approach of those reviewed was, which looks at a database for the actual energy mix of your electricity provider.


The politics of calculators

The "Act on CO2" calculator gives figures for home energy use and travel compared to average domestic emissions. But it does not give overall per capita emissions, which would include public sector emissions and the 'embedded' carbon of services and personal consumption. It reflects therefore a politics of reducing emissions, but without any reference to what level of emissions would represent an equitable global share. 


Carbon rationing and carbon reduction groups

There is a complex argument to be had over carbon rationing. Many environmentalists see personal carbon rations as the only way to achieve an equitable solution to climate change. Others argue that there are obvious reasons why every gram of carbon is not ethically equivalent - still others suggest that such a scheme is simply impractical. There is not room to discuss these arguments here except to say that carbon calculators are an essential tool for groups experimenting in this area.


Carbon confusion

"Carbon emission" figures are sometimes expressed in terms of carbon (C), but more usually carbon dioxide (CO2). Knowing which is crucial when comparing figures because 1 kg of C = 3.67 kg CO2 (or, 1 kg of CO2 = 0.273 kg C).


Carbon Calculators Reviewed

Ethical Consumer reviewed a number of calculators and selected the most useful, while checking for accuracy against standard figures.[7]

For those without Internet access pen, paper and one or more of these resources is easily sufficient.

The great strength of Quaker Green Action'scalculator lies in providing estimates for food, waste, and discretionary spending as well as energy, giving an overall picture in relation to per capita emissions. You can easily combine these estimates with actual figures for transport and domestic energy use using the resources below.

Carbon Counter: Calculate your carbon footprint (Collins Gem, Glasgow 2007) is a useful pocket guide with handy tables on everything from motorbike emissions to journeys to European destinations.

For the basic figures see the Carbon Trust's Energy & Carbon Conversions.

In addition calculators from, and can be downloaded and printed.

Online calculators

The Climate Outreach and Information Network (COIN) conducted a review of online carbon calculators and rated them across a number of areas. It did not assess the accuracy of figures produced.

COIN's top scorer both overall and for land travel was This calculator provides figures for a range of emissions sources otherwise difficult to find, such as wood and butane. Car travel figures are high. Also remember to divide domestic energy figures by the number in your household, as this is not flagged up.

For home fuel COIN recommended (includes heating oil, coal and lpg). took QGA as its starting point. As well as domestic and travel emissions the calculator factors in meat eating, organic/local food, and recycling.

Carbon Gym is useful where exact figures are unknown, or for comparing how specific choices affect the figures. The food section of the calculator produces a range of emissions from best of 0.1 tonnes for a vegan\local\organic to 7.84 tonnes for a meat-addicted supermarket shopper.

Other useful calculators 

CO2 Balance provides a ferry calculator, allowing the user to select ports worldwide and a rail travel calculator using UK train stations.

A no-nonsense number cruncher on a single page - conversions for mains, natural gas, diesel, petrol, lpg, coal, and travel.


Aviation calculators

COIN rated best. However this was partly on the basis that it produces extremely high figures (using an emissions multiplier of around 7). This is well above the normal IPCC range and would have the negative effect of inflating the percentage of emissions saved in a personal carbon reduction scheme achieved by reducing flying.

Atmosfair's emissions calculator was rated as "excellent" by the Tufts Climate Initiative's research[8]. It incorporates a multiplier of 2.7. Extremely easy to use, it provides emissions on an airport-to-airport basis, with the option to include changing planes (which increases overall emissions). Atmosfair was the only calculator found to have this function.

This calculator allows the user to pick airports worldwide using Google Maps. The calculator uses DEFRA figures but there is no aviation multiplier so remember to multiply figures by between 2 and 4.

Part of a wider interactive climate model, is an excellent resource and great educational tool. The calculator even allows for differences between economy and business class. The results are a fascinating range of statistics including the additional cost if aviation fuel was taxed at the same rate as petrol in the UK (about £150 for the UK to New York). If you're interest is actual figures, note that you will get the same CO2 results from Atmosfair a lot easier.



These calculators are good for getting the message across in an easy format.

WWF's calculator asks a range of questions on consumption such as whether you are vegan or vegetarian, giving result as an "ecological footprint".

Simple questions focusing on waste and consumption give an "ecological footprint" in terms of hectares.

Quick and simple estimates from lifestyle questions.


Mobile carbon

For younger users to use on web-enabled mobile phones. Text 'climate' to 80010.


Next generation

These resources involve maintaining an online carbon account and experimenting with personal tradable quotas.

Sign up to the Carbon Account for by far the most sophisticated site that Ethical Consumer found. It tracks your emissions as they change over time, and allows you to compare with other users. The site does not use any estimations of the carbon embodied carbon in, for example, food, but is an exact empirical tool. Tom Dyson, of developers Torchbox Ltd, has ambitious plans for the site, noting that it has been designed to plug into real world inputs such as smart meters. Watch this space.

At the time of writing two other sites were under development offering ongoing "carbon accounts":

Check out Carbon Rationing Action Groups' (CRAGs) website. Here numerous CRAGs in the UK and beyond are recruiting members and holding discussions. Groups agree on their own carbon calculating methodology, a target footprint and a penalty price for kgC over this limit.

Sign up to the RSA's Carbonlimited for discussion and join experiments in online personal carbon trading.


Recommended for specific areas


Public transport

Carbon counter (see Further Reading)

For Train and Ferry


Home Energy



Best Overall Calculators

Calculate online


Related links

See Ethical Consumer's buyer's guide to Carbon Offset Providers.

Standard figures to convert transport and energy types to CO2 can be

downloaded from DEFRA (pdf) has data on the actual fuel mix of UK electricity suppliers. provides car emission figures by model, as well as rating fuel economy A-G.


Further Reading

Chris Goodall "How to Live a Low Carbon Life" Earthscan, London 2007

Mark Lynas "Carbon Counter: Calculate your Carbon Footprint" Collins Gem, Glasgow 2007

Paul Mobbs "Energy Beyong Oil" Cromwell Press Trowbridge, 2005


1 Such as the Crabon Trust's
2 DEFRA produces a figure of 9.4tCOe - this excludes aviation and shipping emissions. The figure of 12.5t is from Goodall, 2007:73
3 'World will face oil crunch in five years,' Financial Times, 09/07/2007
4 'Aviation Emissions and Offsets,' Environmental Change Institute, Oxford University, 2005
5 see Carbon Offset report, Ethical Consumer 106 p.14-15 
6 'Establishing a Code of Best Practice for the Provision of Offsetting to Consumers,' DEFRA, 2007
7 From DEFRA, VCACarFuelData and IPCC
8 'Voluntary Offsets for Air-Travel Carbon Emissions' The Tuft Climate Initiative


First published Ethical Consumer issue 109, Nov/Dec 2007


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