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Conversion factors

Conversion factors guide to help you calculate your organisation’s carbon emissions - with guidance on how to convert energy use and carbon emissions into common units. 

This guide has been updated to use UK Government 2015 conversion factors.

Greenhouse gas (GHG) conversion factors are used to calculate the amount of greenhouse gas emissions caused by energy use. They are measured in units of kg carbon dioxide equivalent**. In order to convert 'energy consumed in kWh' to 'kg of carbon dioxide equivalent', the energy use should be multiplied by a conversion factor.

Conversion factors example

To convert from litres of petrol to kgCO2e emissions multiply by 2.331, so for example:

200 litres petrol = 200 x 2.331 = 466.2 kgCO2e

Carbon emissions are usually quoted in kgCO2/kWh. If you wish to convert the carbon dioxide factors into carbon (ie kgC/kWh), multiply the figure by 12 and divide by 44.

Conversion factors - energy and carbon conversion guide

Our 8-page guide and interactive spreadsheet provides a number of useful conversion factors to help you calculate energy consumption in common units and to work out the greenhouse gas emissions associated with energy use.  

Calculating your energy use and carbon emissions can be useful for monitoring energy use internally within a business, and also for public reporting of energy consumption and carbon emissions.

This guide is based on UK data published by Defra/DECC in June 2015.

Guide contents:

  • Introduction to Greenhouse gas conversions
  • Conversion factors for energy units
  • Energy conversion factors
  • Passenger transport conversion factors
  • Heat content of fuels

The interactive calculator includes:

  • Fuel/energy conversion factors
  • Passenger transport conversion factors (car, bus, rail and air)
  • Heat content of fuels

Publication date Nov 2015; Publication code CTL153.

Conversion factors guide 2015 update (CTL153) - digital download

Purchase your digital copy of the guide (PDF format) & linked interactive spreadsheet (.xlsx).

Price: £14.99

Please contact us on +44 (0)20 7170 7000 or email if you have any problems with ordering online. If you are a current Carbon Trust customer please contact us for your free copy of the publication.

Find out more about our carbon footprinting measurement services and Footprint Certification for your organisation.

For further guidance on conversion factors, see Defra's website.

© 2015 Carbon Trust
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