Flight Emissions Calculator
The carbon emissions of a flight per passenger — with and without the high-altitude effects that roughly double aviation's warming impact.
Emissions per passenger-kilometer depend mostly on how full the aircraft is and how far it flies.
How the flight emissions calculator works
Emissions per passenger-kilometer depend mostly on how full the aircraft is and how far it flies. Short flights are worse per kilometer because take-off and climb burn a disproportionate share of the fuel, so a 500 km hop emits more per kilometer than a 5,000 km leg even in the same aircraft.
The number that surprises people is radiative forcing. Aviation's warming effect is roughly 1.9 times its CO₂ alone, because contrails and nitrogen oxides at altitude add warming that ground-level emissions do not. Reporting standards differ on whether to include it — this page shows both, because quoting only the CO₂ understates the impact by nearly half.
Formula: emissions = distance × factor per passenger-km × class multiplier × (radiative forcing if included)
Worked examples
| Inputs | CO₂ emissions | Note |
|---|---|---|
| A 1,000 km return flight in economy | 316 kg | 316 kg CO₂, or 600 kg with altitude effects |
| A long-haul return in business | 6.82 tonnes | about 6.8 tonnes |
| A family of four, short hop | 632 kg | 632 kg between them |
FAQFrequently asked questions
How much CO₂ does a flight produce?
Roughly 0.15 kg per passenger-kilometer in economy, so a 1,000 km return is about 316 kg — or 600 kg once high-altitude effects are counted.
What is radiative forcing?
Aviation warms about 1.9 times as much as its CO₂ alone, because contrails and nitrogen oxides at altitude add warming. Reporting standards differ on including it; this page shows both.
Why is business class worse?
Because a business seat takes two to three times the floor space of an economy seat, so each passenger carries a larger share of the aircraft.
Are short flights better?
Not per kilometer — take-off and climb burn a disproportionate share of the fuel, so short hops are the least efficient way to fly.
Does offsetting cancel this out?
Only if the offset is real, additional and permanent, which many are not. Treat the figure as the emission, and offsetting as a separate question.
Where these figures come from
- UK DESNZ / DEFRA — Greenhouse gas reporting: conversion factors — the flight, fuel and waste emission factors used here
- Scarborough et al. (2014), Climatic Change — Dietary greenhouse gas emissions — the per-diet daily emission figures
- US EPA — Technical Assistance Document for the Reporting of Daily Air Quality (AQI) — the PM2.5 breakpoints the air quality calculator uses
- US EPA — Greenhouse Gas Equivalencies Calculator — the official US equivalency factors
Last checked: September 2026. Factors are taken from published government and peer-reviewed sources, each named on the page with its year.