Carbon calculator

Put in two places and see the carbon cost of the journey by every mode that runs it, per traveller, alongside how long each one takes door to door. The greener route is usually the slower one, and the hours belong on the same screen as the kilograms.

Milan to Rome

The lowest carbon way to travel from Milan to Rome is by Train, at 15.8 kg of CO2e per traveller. The highest is Flight, at 103 kg, which is 6.5 times as much.

Computed from distance and published factors, not measured.

15.8 kgTrain
16.3 kgCoach
103 kgFlight
11 kgFerryModelled

On this corridor one mode is both the cleanest and the quickest, so there is no trade to make.

Carbon dioxide equivalent per traveller for the whole journey, computed from the distance and a published factor per mode.
Mode	Per traveller	Door to door	Distance	Factor	Basis
Train	15.8 kg	4h	479 km	33 g per passenger km	Trenitalia
Coach	16.3 kg	7h 2m	479 km	34 g per passenger km	BlaBlaCar
Flight	103 kg	4h 12m	493 km	209 g per passenger km	ITA Airways
Ferry	11 kg		479 km	23 g per passenger km	Modelled

Modes with no service on this corridor

This corridor carries no service of this mode, so there is no journey time. The figure applies the same factor to the straight line, which is shorter than any real route, so read it as a floor.

How this is worked out

Computed from distance and published factors, not measured. Every figure here is computed, not measured: the journey distance multiplied by a published emissions factor for the mode, which is the same kind of estimate operators and regulators publish.

Distance. A scheduled row uses the length of the legs the carrier runs. A modelled row uses the straight line between the two places, which no vehicle can follow.

Factors. One figure per mode in grams of CO2e per passenger kilometre, listed in full below with its published basis and the occupancy it assumes. Carbon here is per traveller, so a party of four emits four times one traveller’s figure rather than four times the vehicle’s.

Bands. Air is worked at the short haul figure up to 3,000 km and the long haul figure beyond it. Rail is worked at the European mixed traction average on every service: the high speed figure in the table is applied to no journey.

Flights carry a radiative forcing multiplier of 1.7, the central estimate the UK conversion factor set recommends for the extra warming from emissions released at altitude, and its publisher calls that value significantly uncertain. Both the short haul and the long haul figure carry it, so the two are comparable with each other.

It assumes the occupancy in the table: not the traction mix on the day, not how full the vehicle was, not the weather and not the detour to the station.

These are the factors the rest of the site uses. The figure here and the figure on a route page for the same journey come out of one function, so the two cannot disagree.

The full methodology · The emissions factors dataset

The factor table in full
Factor	g per passenger km	Assumed occupancy	Published basis
`rail`	33 g per passenger km	European fleet average, implied by observed passenger-kilometres	CE Delft for the EEA, table 12.8, EU-27 passenger train 2018, mixed traction, well-to-wheel
`rail-electric-hs`	16 g per passenger km	European fleet average, implied by observed passenger-kilometres	CE Delft for the EEA, table 12.10, EU-27 high speed train 2018, well-to-wheel
`coach`	34 g per passenger km	17.56 passengers per vehicle, the publisher assumption	UK DESNZ 2024, coach, 27.17 direct plus 6.56 well-to-tank, well-to-wheel
`air`	209 g per passenger km	average passenger, the publisher observed load factor across all cabins	UK DESNZ 2024, short-haul average passenger, radiative forcing 1.7x, well-to-wheel
`air-long`	293 g per passenger km	average passenger, the publisher observed load factor across all cabins	UK DESNZ 2024, long-haul average passenger, radiative forcing 1.7x, well-to-wheel
`ferry`	23 g per passenger km	one foot passenger and luggage, no share of the vehicle deck	UK DESNZ 2024, ferry foot passenger, 18.71 direct plus 4.24 well-to-tank, well-to-wheel

Link to the answer

The result is in the address. A link like the one below opens on the answer itself, rendered on the server, with nothing to wait for and no form to fill in again.

https://orlero.com/en-gb/tools/co2?from=milan&to=rome

Put it on your own site

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<p><a href="https://orlero.com/en-gb/tools/co2?from=milan&to=rome">Carbon figures by Orlero</a></p>

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Orlero carbon calculator

The JSON API

The same answer as JSON, for anybody building on it. No key and no sign up.

https://orlero.com/api/tools/co2?from=milan&to=rome&passengers=1&locale=en-GB

from: A city slug, id or name. Required.
to: The same, and not the same place as from. Required.
passengers: A whole number from 1 to 9. Defaults to 1.
locale: One of the sixteen locales this site publishes in, for the place names in the reply. Defaults to en-GB.
Rate limit: Sixty requests a minute per address. Every reply states what is left in its headers, and a request over the line gets a 429 with the seconds to wait.
Licence: CC BY 4.0. Use it anywhere, including commercially, as long as you credit Orlero and link back. CC BY 4.0

The response shape is versioned. Fields may be added; nothing is renamed or removed without the version moving.