How the number is calculated (full transparency)
CO2 = corrected distance (km) × emission factor (kg/passenger-km) × cabin multiplier × RF multiplier (if on) × trips × passengers × flights per year.
| Distance band (corrected km) | Factor kg CO2/passenger-km | Source |
|---|
| Under 550 | 0.246 | BEIS 2022 domestic flight, economy |
| 550 – 3,700 | 0.151 | BEIS 2022 short-haul economy |
| Over 3,700 | 0.148 | BEIS 2022 long-haul economy |
| Cabin class | Multiplier | Basis |
|---|
| Economy | ×1.0 | reference |
| Premium economy | ×1.6 | BEIS long-haul class ratio |
| Business | ×2.9 | BEIS long-haul class ratio |
| First | ×4.0 | BEIS long-haul class ratio |
Distance = great-circle distance between airports plus the ICAO correction for real-world routing: +50 km under 550 km, +100 km for 550–5,500 km, +125 km above 5,500 km. Optional non-CO2 multiplier ×1.44 = DESNZ 2024 with-RF / without-RF ratio (161/112 domestic, 154/107 long-haul g/passenger-km, via UK Parliament Research Briefing CBP-8826). Car equivalence: 0.2485 kg/km from EPA (4.6 t CO2/yr ÷ 11,500 mi/yr). Tree: ≈21 kg CO2/year per mature tree. Home: 14.08 kg/day (EPA equivalencies: 5.139 t/home/yr ÷ 365). Offset price defaults to $15/tonne — illustrative, not a quote.
Honesty box: this is an estimate. ICAO, DEFRA/BEIS, myclimate and airline calculators use different fuel-burn models, load factors, and RF treatments — their answers for the same flight can differ by 2–3×. Use this tool to compare choices (economy vs business, direct vs connecting), not as an exact footprint.
Frequently asked questions
How are flight emissions calculated?
This calculator multiplies corrected flight distance (km) × emission factor (kg CO2 per passenger-km) × cabin multiplier × optional non-CO2 (RF) multiplier × trips × passengers × flights per year. The distance is the great-circle distance between your airports plus the ICAO correction for real-world routing (+50 km under 550 km, +100 km for 550-5,500 km, +125 km above 5,500 km). Every factor used is named on this page.
What emission factors does this calculator use?
The distance-based factors come from the UK BEIS 2022 'Greenhouse gas reporting: conversion factors' air-travel rows, economy class, without radiative forcing: 0.246 kg/passenger-km under 550 km, 0.151 for 550-3,700 km, and 0.148 above 3,700 km. Cabin multipliers (1.0 / 1.6 / 2.9 / 4.0 for economy / premium economy / business / first) come from the BEIS long-haul class ratios. The methodology is labeled, not hidden.
What is a typical London-New York flight's footprint?
Using this calculator: London (LHR) to New York (JFK) is 5,540.51 km great-circle, corrected to 5,665.51 km. Round trip, economy, without the non-CO2 option: 838.50 kg per leg, 1,676.99 kg total (≈1.68 tonnes). That's roughly 6,748.45 km of average car driving, 79.86 tree-years of absorption, or 119.11 days of average US home electricity — and about $25.15 to offset at $15/tonne. Same flight in business class: 4,863.27 kg.
What about a short hop like Jakarta-Singapore?
Jakarta (CGK) to Singapore (SIN) is 884.03 km great-circle, corrected to 984.03 km. Round trip in economy: 148.59 kg per leg, 297.18 kg total — about 1,195.88 km of car driving, 14.15 tree-years, 21.11 days of home electricity, and $4.46 to offset at $15/tonne. Short flights carry the highest per-km factor (0.246) because takeoff and climb dominate.
How much worse is an ultra-long-haul with non-CO2 effects?
Sydney to Los Angeles round trip, economy, with the non-CO2 (RF ×1.44) option: 2,597.04 kg per leg, 5,194.08 kg total (≈5.19 tonnes) — roughly 20,901.71 km of car driving, 247.34 tree-years, 368.91 days of home electricity, and $103.88 to offset at $20/tonne. First class with RF on the same route would be about 9,659.47 kg (London-New York example).
What does the 'non-CO2 warming effects (RF)' option do?
Planes warm the climate through more than CO2: contrails, nitrogen oxides, and soot at altitude. This toggle multiplies the CO2 result by 1.44, the DESNZ 2024 with-RF / without-RF ratio (161/112 g per passenger-km domestic, 154/107 long-haul, published via UK Parliament Research Briefing CBP-8826). It is an estimate of extra warming, not measured exhaust chemistry — published RF treatments are the main reason calculators disagree.
Why does cabin class change the result so much?
The fuel burn is the plane's, and it is divided among passengers by floor area: a business or first-class seat occupies far more space than an economy seat, so fewer passengers share the fuel. That is why BEIS assigns business ×2.9 and first ×4.0 on long-haul. Choosing economy over business on a long-haul round trip roughly thirds your share.
What is the car-driving equivalence based on?
The US EPA's Greenhouse Gas Equivalencies Calculator: a typical gasoline passenger vehicle emits about 4.6 metric tons of CO2 per year driving around 11,500 miles per year — 400 g per mile, i.e. 0.2485 kg per km. So 1,676.99 kg of flight CO2 ÷ 0.2485 = 6,748.45 km of driving. One-passenger car trip basis.
What are the tree and home equivalences based on?
Tree-years use the commonly cited figure of about 21 kg of CO2 absorbed per mature tree per year. Home-electricity days use the EPA equivalencies figure of 5.139 metric tons of CO2 per US home per year ÷ 365 = 14.08 kg per day. They are illustrations to make tonnes relatable, not exact trades.
How is the offset cost estimated?
Tonnes of CO2 × the price you enter (default $15 per tonne). The default is illustrative — retail carbon offsets commonly range from a few dollars to tens of dollars per tonne depending on project type and certification (Gold Standard, Verra). Edit the price to match a program you are considering; the number is not a quote.
How accurate is this? Why do different calculators disagree?
It is an estimate. ICAO uses a fuel-burn model per aircraft type, DEFRA/BEIS uses distance bands, myclimate adds its own RF treatment — and load factors, aircraft age, and routing vary per flight. Published tools can disagree by 2-3× on the same itinerary. This page states its methodology so you can compare choices (economy vs business, direct vs connecting) rather than treating one number as truth.
Do connecting flights or frequent flying change the result?
Yes. Two shorter legs emit more than one direct flight on the same city pair, because each takeoff burns a lot of fuel — enter each leg separately for an honest total. The 'flights per year' field multiplies the result so frequent flyers see their annual footprint, e.g. 4 yearly London-Paris round trips in economy = 780.99 kg per year.