How the flight carbon emissions calculator works

Our flight carbon calculator estimates the carbon dioxide emissions from your flying based on the number and distance of the trips you take.

The calculator uses a number of assumptions to come up with this estimate, so the final amount should be regarded as a general guide rather than a precise figure. Our assumptions are based on the greenhouse gas emissions protocols developed by the World Resource Institute.

We start by calculating the distance between your origin and destination city, based on their latitude and longitude. This is a standard trigonometric calculation, and we ignore any stopovers you might make along the way. If you wish to calculate the effect of stopovers, simply enter the legs of the flight as separate trips.

Next we categorize your flight as a short-, medium-, or long-haul trip. Because planes burn more fuel at takeoff and landing than at cruising altitude, short-haul trips are less fuel-efficient per mile flown.

For each of the three types of trips, we use a different carbon index that indicates the amount of fuel burned, on average, per mile of the journey. By multiplying this index by the distance of your trip, we determine how much fuel was burned per passenger for that particular flight.

The carbon index is just an approximation based on industry averages. The actual amount of fuel burned per passenger per mile depends on the type of plane, the number of people flying, the weight of the cargo, and other factors.

But on average, the resulting flight emissions profile provides a good approximation of the global warming impact of your flying. Chances are, it's bigger than you thought.