Flights are the fastest way to destroy a trip's carbon budget. See exactly what surface travel costs the atmosphere instead — and what that difference means.
By Sloth generates realistic overland itineraries with booking links, journey times, and confidence ratings — no flights, by design.
This calculator uses published emissions data — no proprietary models, no black boxes.
| Mode | Emissions factor | Source |
|---|---|---|
| Flight (economy) | 0.195 kg CO₂e / passenger-km | ICAO Carbon Emissions Calculator — includes radiative forcing index (×2 multiplier) to account for high-altitude warming effects beyond CO₂ alone |
| Train (blended) | 0.035 kg CO₂e / passenger-km | EEA transport data — blended average across European diesel and electric networks |
| Bus / coach | 0.027 kg CO₂e / passenger-km | Eurostat / EEA |
| Ferry | 0.190 kg CO₂e / passenger-km | EEA — ferries are relatively emissions-heavy; flagged where relevant |
| Overland (blended) | 0.028 kg CO₂e / passenger-km | Weighted average: ~60% train, ~35% bus, ~5% ferry. Actual trips vary by region — rail-heavy European routes are much lower; bus-heavy Central Asian routes slightly higher. |
Distance: Flight distance is calculated as the great-circle distance between the two cities (the theoretical straight-line path through the air). Overland distance is estimated at 1.3× the flight distance — a typical rail/road factor for non-direct routes.
Radiative forcing: The flight figure includes a 2× RFI multiplier. Aviation has warming effects beyond CO₂ (contrails, NOₓ, water vapour) that operate at altitude. Without this multiplier, flight looks 50% "cleaner" than it is. Some calculators omit it — we include it because it reflects real-world impact more accurately.
Limitations: Emissions vary significantly by airline, aircraft type, occupancy, and grid mix of the region's rail network. This is a planning-level estimate, not a precision audit.