Calculating a car’s CO2 emissions from its mpg

Motorists who drive cars that were first registered before 2001 are unlikely to be aware of how much CO₂ their vehicle emits.

A car’s V5 document (sometimes referred to as the logbook) details the amount of CO₂ the vehicle emits per kilometre, but this is not the case for vehicles registered before 1st march 2001.

How to calculate CO₂ g/km from mpg

If you know a car’s mpg figure, you can use a simple calculation to work out its CO₂ g/km figure.

The calculation is simple, but you may find it helps to use a calculator.

A spokesperson for the Environmental Transport Association (ETA) said: “Now that road tax is calculated on the basis of CO₂ emissions, an increasing number of people know how their car emits, but this may not be the case for the owners of older cars.”