How do you calculate offsets for my flight?

The calculations we use are based on a report on the climate impacts of aviation by the Environmental Change Institute at Oxford University - Aviation Emissions and Offsets. Four factors are assessed in our calculator:

* The fuel consumption rate of the aircraft being used.
* The seats occupied and freight on-board;
* The overall impact of GHG emissions in the stratosphere (i.e. a multiplier for the altitude at which emissions are released); and
* The distance flown.

Thus, in calculating emissions for a passage on long haul flight we take the average fuel burn figures for a Boeing 747 and an Airbus A360 as published by the EU. We divide this by the average total number of seats (not occupied seats). We then subtract fuel use for freight carried on the average long haul aircraft. GHG impacts in the upper atmosphere are estimated to be double the amount of CO2 emissions. We double the fuel CO2 and finally multiply this GHG emission rates by the great-circle distance between departure and arrival airports.

For short haul flights we use a similar method to the above, but use the fuel consumption for a Boeing 737 as the reference aircraft.

As we gain access to more sophisticated databases on aircraft serving each route and the number of seats occupied we will continually refine our calculator to reflect emissions associated with your flight.