Travel Carbon Footprint Calculator

Transportation is one of the largest sources of personal carbon emissions. Different modes of transport have dramatically different carbon intensities per passenger-kilometer.

CO2 emissions per passenger-km (approximate averages):

• Short-haul flight (under 1,500 km): 255 g CO2e/km, the worst per kilometre, because takeoff and climb burn a large share of the fuel over a short distance
• Long-haul flight (over 1,500 km): 195 g CO2e/km, more efficient per kilometre, though the sheer distance makes the trip total far higher
• Economy class vs business class: Business uses 2.7× more carbon due to seat space allocation
• Car (average ICE, single occupant): 192 g CO2e/km
• Car (2 people sharing): 96 g CO2e/km
• Car (4 people): 48 g CO2e/km
• Electric vehicle (average US grid): 70 g CO2e/km
• Intercity bus (coach): 27 g CO2e/km
• Intercity train (average Europe): 14 g CO2e/km
• High-speed train (TGV France): 3 g CO2e/km (nuclear electricity)
• Bicycle / walking: 0 g CO2e/km

Radiative forcing (flights): Flights at high altitude have a warming effect 2–4× greater than just the CO2 emitted, due to contrail formation and NOx emissions. This calculator includes a standard radiative forcing factor of 1.9× for flights.

Context for your emissions:

• Average global per-capita annual CO2 budget (1.5°C target): ~2,000 kg CO2e/year
• A round-trip London to New York flight (11,110 km): ~2,170 kg CO2 alone, or ~4,120 kg CO2e once the 1.9× radiative forcing is applied. That single trip is roughly twice the entire annual budget above.
• A 500 km car journey alone: ~96 kg CO2e
• Taking the train for 500 km: ~7 kg CO2e

Why published flight figures differ so much: If you check that London to New York number against an airline’s own calculator you may see something closer to 1,000 kg, and against ICAO’s tool lower still. The spread is real and it comes from three choices, none of them hidden but none of them standard either. First, whether radiative forcing is counted at all: including contrails and NOx roughly doubles the figure, and many published tools quietly omit it. Second, the assumed load factor and aircraft type, which move the per-passenger figure by a third either way. Third, whether freight carried in the hold is allocated a share of the fuel. This page counts radiative forcing at 1.9× and uses a mid-range 195 g per passenger-km for long-haul, which puts it toward the higher end of published estimates. Treat any flight figure, including this one, as accurate to roughly a factor of two rather than to three significant digits.

Offsetting: Tree planting offsets ~21 kg CO2 per tree per year. That transatlantic round trip would need about 196 trees growing for a full year to absorb it. High-quality carbon offsets (Gold Standard) cost roughly $10–$30 per tonne CO2, though offsetting is a poor second to not flying: the emissions happen now and the absorption takes decades.