There are many carbon calculators available on the internet which can help make an initial calculation of a business's carbon footprint. These business calculators typically require data on annual energy consumption, fuel consumption of company vehicles and details on business travel. Most use definitions provided in the GHG Protocol covering direct GHG emissions, indirect GHG emissions from electricity and travel emissions. They do not, however, help incorporate supply chain emissions.

These calculators are primarily from the UK or US and focused on small to medium- sized business. Some offer additional services to build online carbon calculators for larger companies.

The Carbon Trust
http://www.carbontrust.co.uk/footprintcalculator

The Carbon Trust’s new business carbon footprint calculator enables businesses to quickly quantify their key carbon impacts and understand where action might be required to reduce emissions. It introduces common footprinting concepts in line with widely accepted reporting approaches such as the Green House Gas (GHG) Protocol.

The Clean Planet Trust
http://www.puretrust.org.uk/Business/Calculator.aspx

PURE is a registered charity which supports the UK Government Code of best practice for carbon offsetting.

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Carbon UK
http://www.carbonuk.co.uk/carbonemission.asp

Carbon UK has developed a simple calculator of CO2 impact based on the conversion data issued by Department of Environment, Food and Rural Affairs as part of its Environmental Reporting Guidelines (DEFRA).

Carbon Passport
http://www.carbonpassport.com/For%20business/Business%20calculator

A business calculator designed to calculate organization CO2 emissions via 5 business categories; flights, mileage, travel, energy consumption of premises, and miscellaneous usages.

The Carbon Neutral Company
http://www.carbonneutral.com/sbc/index2.asp

A carbon calculator primarily designed for businesses that have fewer than 100 employees, and have a maximum of 5 sites.

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C Level
http://www.clevel.co.uk/business-calc.htm

A basic UK-based business calculator, with additional support for complex organization structure offered.

NEF
http://www.nef.org.uk/greencompany/co2calculator.htm

A carbon calculator for use by UK organizations based upon the recommended conversion factors provide by (DEFRA).

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ClimateCare
http://www.climatecare.org/business/business-co2-calculator

A UK-based business calculator

Ecoforests
http://carbon.ecoforests.org/

A carbon calculator for use by UK organizations based upon the recommended conversion factors provide by (DEFRA).

Green Power Equivalence Calculator Methodologies
http://www.epa.gov/greenpower/pubs/tools.htm

A number of calculations tools are available from the Green Power Partnership sponsored by the United States Environmental Protection Agency.