Trip carbon footprint calculator for car, train, plane, or bus

Enter the distance in kilometres, choose car, train, plane, or bus, and receive the estimated kilograms of CO2e together with the factor used. It is useful for comparing realistic journey options, preparing a travel report, or adding a consistent estimate to an application. The result is an indicative passenger-travel estimate, not a complete lifecycle assessment or a measurement of one specific vehicle.

Start with the distance that matches your decision

A useful estimate begins with a distance that represents the journey you actually want to assess. Enter kilometres for one direction if you are comparing one-way options, or add both directions before estimating a return trip. If a route includes several legs, you can calculate each leg separately and add the resulting kilograms of CO2e, especially when the transport mode changes along the way. The calculator treats distance as passenger travel, so the result represents one traveller using the selected mode. It does not infer road routing, airport connections, transfers, or detours; supply a distance that already includes those details when they matter. For a fair comparison, use the same origin, destination, and trip boundaries for every mode. A rail distance and a road distance may differ even between the same cities, while a flight estimate may need the actual flown or published route distance rather than a straight line on a map. Clear boundaries make the comparison repeatable and prevent an apparently precise result from hiding inconsistent assumptions.

Understand the factor-based calculation

The calculation multiplies the supplied kilometres by a fixed emissions factor for the chosen mode. The factors are expressed as kilograms of CO2e per passenger-kilometre: 0.171 for car, 0.041 for train, 0.246 for plane, and 0.104 for bus. CO2e combines climate effects into a common carbon-dioxide-equivalent unit, which makes broad comparisons easier. The response includes the factor as well as the total, so the assumption remains visible in reports and automated workflows. These are standard representative factors, not claims about every operator, vehicle, fuel, route, or occupancy level. A full car can have lower emissions per passenger than a car carrying one person; an electric train depends on its electricity mix; and aircraft results vary with distance, load, cabin class, and operational conditions. The estimate therefore works best as a consistent screening figure. It helps answer which option is likely to have the smaller footprint under one shared method, while a supplier-specific inventory may require audited factors and more detailed activity data.

Use the result responsibly in comparisons and reporting

Read estimated_co2e_kg as an indicative total for the distance and mode you submitted. Keep distance_km, mode, and emission_factor_kg_co2e_per_km beside that total whenever you store or publish it; those fields explain how the number was produced and make later recalculation straightforward. When comparing alternatives, run one request per mode with the appropriate route distance, then compare the totals rather than comparing factors alone. The lower factor does not always guarantee the lower trip total if the routes have very different lengths. For recurring travel, multiply or sum individual trip results outside the calculator, preserving each trip's boundaries so you can audit the total. Avoid describing the output as an exact measurement, a verified offset amount, or a complete organisational inventory. It excludes vehicle manufacture, infrastructure, accommodation, local transfers not included in the distance, and other indirect effects. The API costs $0.002 per request and uses the same deterministic calculation every time, making it suitable for spreadsheets, booking comparisons, internal dashboards, and repeatable estimation workflows where transparent assumptions matter more than false precision.