Our numbers and formulas

To compare the environmental impact of different transport modes, we use $C{O}_2$-equivalents ($C{O}_{2}e$) — a common unit that captures the effect of multiple greenhouse gases like methane $C{H}_4$ and nitrous oxide $N_{2}O$ as if they were all $C{O}_2$. This makes it easier to calculate and compare emissions across cars, buses, trains, and flights. This is the general formula for calculating the $C{O}_2$ emissions. We multiply the $C{O}_{2}e$ equivalents with the number of kilometers traveled. Some of the transport methods use this simple formula, whilst others have small variable changes.

This is the core formula used in our calculator. We multiply the number of kilometers traveled by an average emission factor for each mode of transport. These emission factors are based on grams of CO₂e per kilometer, and they vary depending on whether you're driving a diesel car, taking a train,or flying.

Some transport methods have emission factors that already account for sharing. For example, a train or flight gives emissions per passenger. For others, like a car or ferry, we divide the total emissions across all passengers to get a fairer estimate per person.

Example Calculation

Let's say you drive 50 kilometers in a petrol car. The emission factor for a petrol car is approximately $160{\text{g CO}}_{2}e/\text{km}$.

So, this journey results in a total emission of $8{\text{kg CO}}_{2}e$.