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Home > Existing Buildings > CO2 Calculator

Simple Carbon Calculator

Now includes 2015 data

Calculate your CO2 with our easy to use calculatorThis page contains a simple carbon calculator for use by UK organisations based upon the June 2015 recommended conversion factors provided by Defra as part of its Environmental Reporting Guidelines. If you want to use 2014 data (for reporting on 2013 comparative figures) the old factors can be found in our 2014 calculator.

Calculate your footprint

This is a free simple calculator designed to enable estimated carbon footprints to be calculated by most UK organisations. If you need a more sophisticated service, or help in setting the boundary or scope of your calculation, we can also offer more comprehensive help and support on a paid-for basis, as described on our Carbon Footprinting Services page.

1. First select the best description of the electricity source from the drop down below. You can specify two sources; if in doubt use "Average UK Grid Electricity". Note that although UK emissions are in kgCO2e, for other countries they are only in kgCO2, not taking into account any associated emissions of methane or nitrous oxide. And if you want to calculate emissions from road transport using miles, use the third list to select type, size and fuel of vehicle used. There are separate factors in the main table for trains, buses and aeroplanes. For flights, there's a list by class and general distance - short haul would typically be within Europe or North America and long haul intercontinental. Note that distances are per passenger mile - some tickets quote distances in km.
Main source of electricity:
Second source of electricity:
Type of car/bike used for mileage estimates:
Distance & class of air trip used:

2. Now type the energy value from your bill or records into the left column. Then click anywhere outside the cell you just filled. The answer will appear in the column to the right
 Energy Value
Conversion Factor
Building or Process Energy Values
kWh electricity (main source)
(See notes)
kWh electricity (second source)
(See notes)
kWh natural gas
* 0.18445 =
therms natural gas
* 5.406 =
litres domestic heating oil (kerosine)
* 2.53215 =
litres heating oil (gasoil)
* 2.90884 =
litres of propane/butane
* 1.50938 =
tonnes of heavy fuel oil
* 3,223 =
tonnes of coal
* 3,065 =
tonnes of wood pellets
* 68 =
Transport Energy Values
litres of petrol
* 2.1944 =
litres of diesel
* 2.5839 =
litres of Auto LPG
* 1.50938 =
miles in a car/taxi/bike
(see above)
miles on a train, tram, tube or coach
* 0.073 =
miles on Eurostar
* 0.019 =
miles on a local bus
* 0.161 =
miles in an aeroplane
(see above)
Optional Extra Data:
Floor Area (m2) No. of Staff

Energy used in buildings & processes:

Total Energy: kWh

Energy per m2 Energy per Employee kWh
Building Use

Total emissions: kgCO2e

equivalent to kg Carbon

Help and Advice

We may be able to offer limited help and advice, without charge, if you send an e-mail to, but this is limited by staff availability. We can also offer more comprehensive help and support on a paid-for basis, as described on our Carbon Footprinting Services page.

Please don't use this simple calculator for statutory reporting under Climate Change Agreements of the new CRC Energy Efficiency Scheme. A table of factors to apply for the CRC will be found on the Environment Agency's website, although they are not listed in the May 2015 scheme guidance document.

All figures, except international electricity emissions, include the incremental emissions due to other GHGs such as CH4 and N2O, so they are compatible with Scope 1 or Scope 2 emissions reporting under the GHG Protocol. They still exclude emissions associated with the production of fuels, such as oil refining or fuel distribution, so are not suitable for well to tank (WTT) or Scope 3 reporting.

Which electricity factor should we use?

This table offers a number of factors for converting electricity to its carbon dioxide equivalent. The default one is recommended unless you have a good reason to use another factor: the average figure is uses the total UK electricity generation mix of coal, nuclear and gas turbines, as well as renewables. Previously this was based on a 5 year rolling average, to smooth out year on year changes caused by factors such as the operating performance of nuclear power stations and the latest developments in wind energy. From 2013, the prior year figure has been used, as it is a better indicator or the current generating mix. For 2014 we have added one that includes transmission and distribution losses (for the UK only), which is the combined total of GHG Protocol Scope 2 and Scope 3 emissions.

For electricity generated from renewable sources, zero carbon dioxide emissions may be used if the supply has been generated onsite. It was formerly acceptable to use zero for electricity bought on a certified green tariff, but in 2008 Defra decided that green tariffs should be reported using the same factor as for average grid electricity. Although we allow a zero factor for onsite renewables generated, this should only be used if REGOs are not traded. However for the reverse calculation back to energy, we have omitted renewables from the kWh totals. If you use onsite CHP, you will need to use a more sophisticated tool.

For other countries, the electricity component would need to be adjusted based upon primary fuel mix. Defra now publishes a table of factors for 56 countries - only a few key countries where Britons have holiday homes or major manufacturing centres are included above. Note these factors can change significantly from year to year based on estimation methods and so are now quoted to 3 significant fiugures, not 5.

What do these figures mean?

Around half UK CO2 emissions come from industry and commerce, including the use of transport to deliver goods. This calculator should help smaller companies identify their carbon footprint, based on available records of energy used. Larger organisations, which have already taken steps to reduce energy use and their carbon footprint, are advised to find out more about the Carbon Trust Standard, which uses a more sophisticated carbon calculation.

How do they compare with household emissions?

Although this calculator was designed for use by small offices, it can easily be used to produce a figure for household emissions. Ignoring transport emissions, estimates by DECC in the English National Energy Efficiency Database (NEED) suggest that a typical (median) annual energy use for natural gas is around 13,260kWh and 3,380kWh for electricity. These are based on a rolling 5 year average from 2009-13 and are slightly lower than the regulator Ofgem estimates, but may reflect the trend towards much higher efficiency boilers since it became compulsory to install only condensing models. This equates to 4.008tCO2 per annum, but excludes any contribution from oil, LPG or solid fuels. This typical value also excludes the distorting effect of a few very large or badly insulated homes, which increase the average (mean) value. If we take 2013 mean figures, and adjust for homes heated by oil, coal or biomass, the average domestic consumption rises to around 21,900kWh in total, producing around 4.77tCO2. On either measure they are quite a bit lower than our earlier estimates of around 4.85tCO2 which was based on 2008 data.

Although we won't go into per capita emission estimates here, these have also fallen in recent years, in part due to the tendency for car mileage to have plateaued, for cars to become more fuel efficient (even as petrol has substantially been replaced by diesel). The one area that continues to rise relates to international air travel.

Where do these figures come from?

All data in this CO2 calculator is based upon the official 2014 guidelines from the Department of Environment, Food and Rural Affairs, originally published in 2001, with data updated at June 2015. Emissions for other fuels can be found on Defra's Environmental Reporting page. This table only gives our selection of the most useful conversion factors, and CO2 equivalents are given on a Gross Calorific Value basis: Defra may eventually move to a net CV basis which will slightly increase emission factors from natural gas and LPG.

The average car mileage figure when size and fuel are unknown is equivalent to an average UK family car returning 36mpg. This too is considerably more fuel efficient than earlier factors, reflecting the better fuel economy of the UK fleet as a whole. We have (from 2013 onwards) added additional types, sizes and fuels to enable a better estimate of emissions. If your car fleet returns better figures on average, (or you drive a smaller car achieving (say) 45mpg, or regularly share a car) then you could adjust the mileage accordingly to estimate CO2 emissions. In choosing a figure, it's worth bearing in mind that official published fuel consumption figures are calculated under ideal conditions (a warmed up engine, no sharp braking or accelerating) and are typically 15% better than achieved by most drivers in real life with a larger difference for newer more fuel efficient cars. Petrol and diesel emissions are based on UK retail blends, which typically include a small proportion of biofuels. The average diesel car has only slightly lower emissions due to it typically being significantly larger. Taxi emissions are based on average passenger-km emissions in a typical black cab (so make allowance for sharing).

Aeroplane emissions are very hard to estimate. The figure above is based upon short-haul (European) flights in economy class - add up to 50% for business class travel with lower seat densities. The 2013 figures now include an estimate of radiative forcing from other aircraft emissions in the upper atmosphere, such as ozone created from NOx or condensation trails, and not just the CO2 emitted on the journey.

Rail and local bus emissions vary greatly depending on time of day (how busy the bus or train is), and location - lightly used rural buses inevitably report higher emissions than ones in central London. We have used a network rail average, though commuter trains may have lower emissions. From 2013 we have added Eurostar as a lower-carbon alternative to flying, though our kWh estimate is a bit flaky. One reason its emissions are low is that it is quite largely powered by French (nuclear) electricity. Coaches (long distance bus) are generally calculated to have emissions even lower than rail, but are included with trains.

If you are still uncertain about your footprint, or would like to get a more accurate estimate, including advice on how to manage your footprint, then we can also offer more comprehensive help and support on a paid-for basis, as described on our Carbon Footprinting Services page.

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