Travel Carbon Footprint Calculator
Estimate the CO₂e of a trip across flights, car, train and coach — by cabin class, car occupancy and round trips — using the UK Government / DEFRA emission factors.
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Estimates based on the UK Government / DEFRA greenhouse-gas conversion factors (kg CO₂e per passenger-km; per vehicle-km for cars, divided by occupants). Real emissions vary with load factor, routing, occupancy and energy mix — treat figures as approximate. With radiative forcing on, flight figures include a ~1.9× uplift for high-altitude non-CO₂ effects.
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What’s the carbon footprint of my trip?
Multiply each leg’s distance by its emission factor: roughly 0.12 kg CO₂e per km for a long-haul economy flight, 0.15 for short-haul, about 0.17 per vehicle-km for a petrol car (shared between occupants), and just 0.035 per km by train. A 5,000 km long-haul return in economy works out around 2.2 tonnes with high-altitude effects included — close to half an average person’s entire yearly footprint. Enter your legs above for your own total.
Methodology: Factors are from the UK Government / DEFRA greenhouse-gas conversion factors, in kg CO₂e per passenger-km (per vehicle-km for cars, divided by occupants): long-haul flight 0.11704, short-haul 0.151, domestic 0.246 (economy), with cabin-class multipliers (premium 1.6×, business 2.9×, first 4×) and an optional ~1.9× radiative-forcing uplift for non-CO₂ high-altitude effects; national rail 0.03546; coach 0.027; cars 0.05–0.17 per vehicle-km by fuel. The short/long-haul split is DEFRA’s 3,700 km cut-off. These are averages and real emissions vary with load factor, routing, occupancy and the electricity grid, so totals are approximate. How we test & calculate.
What a trip really costs the climate
Most of a trip’s carbon comes from getting there, and the choice of mode swings the answer enormously. This calculator adds up the legs of a journey — a flight, a hire car, a train, a coach — and gives a single per-person figure in CO₂-equivalent, with a breakdown so you can see where the weight sits. It uses the UK Government / DEFRA emission factors, the same dataset that sits behind most credible travel calculators, so the numbers are grounded rather than guessed.
Flights dominate — and the details matter
For almost any mixed trip, the flight is the largest slice. A long-haul economy flight is around 0.12 kg CO₂e per km, short-haul nearer 0.15, and a domestic hop higher still per km because take-off and landing dominate a short flight. Two choices move the number a lot: cabin class (business is roughly 2.9× economy, first around 4×, because each seat claims more of the plane) and whether you include radiative forcing, the uplift for the extra warming caused at altitude. You can compare the flight itself in more detail with the flight time & CO₂ tool.
Cars, trains and the power of sharing
A car’s emissions are counted per vehicle, then split between everyone in it — so a petrol car at roughly 0.17 kg per km shared by four people is a quarter of that each, which can undercut the train for a full car. Trains are the low-carbon backbone of European travel at about 0.035 kg per passenger-km, and coaches are lower still. Where a route is feasible by rail, it’s almost always the greener call. If you’re also driving, the fuel cost calculator pairs the money side with the carbon side.
An honest estimate, not an exact figure
Every factor here is an average. A full flight is more efficient per head than an empty one; an electric car is only as clean as the grid charging it; routing and weather shift real fuel burn. So treat the total as a well-grounded estimate for comparing options — flying versus the train, economy versus business, sharing the car versus not — rather than a precise carbon account. The relative differences are the part you can trust, and they’re usually large enough to guide a decision.
Frequently Asked Questions
How is the carbon footprint calculated?
For each mode, the distance is multiplied by a published emission factor in kilograms of CO₂-equivalent per passenger-kilometre — or per vehicle-kilometre for cars, then divided by the number of occupants. The factors come from the UK Government / DEFRA greenhouse-gas conversion dataset, which is the same source most reputable travel calculators use. The tool sums the modes for a per-person total and shows the split between them.
Why are flights so much higher than trains?
Two reasons. Flying burns a lot of fuel per passenger — roughly 0.11 to 0.25 kg of CO₂ per km depending on the flight length — while a national rail journey is around 0.035 kg per km, several times lower. On top of that, emissions released at altitude have extra warming effects beyond the CO₂ itself. So for a route you could take by train, the train is almost always the far lower-carbon choice, which is why the breakdown bar usually shows the flight dominating a mixed trip.
What is radiative forcing, and should I include it?
Aircraft emit not just CO₂ but water vapour, nitrogen oxides and contrails high in the atmosphere, which add to warming. Radiative forcing is the adjustment that accounts for those non-CO₂ effects — commonly applied as roughly a 1.9× uplift on the flight figure. Including it gives a fuller picture of a flight’s real climate impact, so it’s on by default here; turn it off if you want the CO₂-only number that matches the bare DEFRA factor.
Does cabin class really matter?
Yes, a lot. A business or first seat takes up far more space and weight per passenger than economy, so its share of the flight’s emissions is much larger — DEFRA assigns business roughly 2.9× and first around 4× the economy figure, especially on long-haul. Flying economy is one of the simplest ways to cut the footprint of a flight you’re going to take anyway.
How accurate is this?
It’s a solid estimate, not a precise measurement. The factors are averages, so real emissions for a specific aircraft, route, load factor or car will differ — a full flight is more efficient per passenger than a half-empty one, and an electric car’s footprint depends heavily on the local electricity grid. Use the figures to compare modes and choices rather than as an exact accounting, and treat the totals as approximate.
How can I reduce my travel footprint?
The biggest levers, roughly in order: take the train instead of flying where it’s feasible; avoid very short flights, which are the most carbon-intensive per km; fly economy and direct (each take-off and landing adds emissions); fill the car with passengers to split its footprint; and combine trips so one journey does more. Offsetting can come after that, but reducing the emissions in the first place matters far more.