Travel Carbon Footprint Calculator
Treading lightly starts with knowing the number. Add each leg of a journey and see how the mode you choose changes the footprint — often more than the distance does.
Estimated footprint
| Leg | Distance | CO₂e |
|---|---|---|
| Flight (long, ≥1500 km) | 1800 km | 351 kg |
| Train | 300 km | 12.3 kg |
How the footprint is calculated
Each leg’s footprint is its distance multiplied by an emission factor for the mode, measured in kilograms of CO₂-equivalent per passenger-kilometre. Public-transport factors are already per-passenger, so the passenger field does not change them. A car’s factor is per vehicle, so the tool divides it by the number of people aboard — the one lever that most changes a road leg.
The legs are summed for a trip total, and that total is divided by a rough annual absorption rate for a tree to express it as tree-years. The comparison built into the tool is the real lesson: put a short flight next to the same distance by train and the case for the slower option makes itself.
Frequently Asked Questions
Where do the emission factors come from?
The tool uses representative average figures for grams of CO₂-equivalent per passenger-kilometre, in the range widely cited by transport agencies and carbon-reporting bodies: long-haul flying is a little lower per km than short hops because cruise is efficient relative to take-off; rail and coach are dramatically lower; a car sits between them and improves sharply as you fill its seats. They are averages, not a measurement of your specific vehicle or flight.
Why does sharing a car cut its number so much?
A car's emissions come from the vehicle, not the person, so they are fixed whether one or four people ride. The calculator divides a car leg's total by the number of passengers, which is why a full car can rival a train per head while a solo drive is one of the least efficient ways to cover a long distance.
Is the train really that much better than flying?
Over comparable distances, yes — rail typically emits a small fraction of a flight's per-km footprint, and swapping a short-haul flight for a train is one of the single biggest reductions an individual traveller can make. Enter the same distance for both modes and the gap is stark.
What does 'tree-years to offset' mean?
It is an intuitive yardstick, not a precise offset scheme. A maturing tree absorbs on the order of twenty-odd kilograms of CO₂ a year, so dividing your total by that figure gives a rough sense of scale. Real offset programmes vary widely in quality; treat the number as a way to feel the size of a trip's footprint, and prioritise reducing it over offsetting it.
Educational estimate only. Emission factors are broad averages; actual emissions depend on the aircraft, load factor, route, and vehicle. Use the figure to compare options, not as a certified measurement.