This handy little online fuel usage & CO2 Calculator, helps you work out your average fuel consumption costs and Carbon Dioxide emmissions based on fuel usage. You can use Either Litres, Imperial Gallons Or US Gallons.

You can always find the most up-to-date average UK Fuel prices from the AA here

Calculating CO2 emissions

The Intergovernmental Panel on Climate Change (IPCC)  guidelines for calculating emissions inventories require that an oxidation factor be applied to the carbon content to account for a small portion of the fuel that is not oxidized into CO2. For all oil and oil products, the oxidation factor used is 0.99 (99 percent of the carbon in the fuel is eventually oxidized, while 1 percent remains un-oxidized.

Finally, to calculate the CO2 emissions from a gallon of fuel, the carbon emissions are multiplied by the ratio of the molecular weight of CO2 (m.w. 44) to the molecular weight of carbon (m.w.12): 44/12.