Compare CO₂e and travel time for the same trip by car or by bike.
| Car kg CO₂e | – |
| Bike kg CO₂e | – |
| Saved kg | – |
| Car minutes | – |
| Bike minutes | – |
Use this calculator for a commute or a shop run when you want both the CO₂ difference and a rough time difference at the speeds you actually ride and drive.
The calculation is: kg = distance × grams per km / 1,000. Minutes = distance ÷ speed × 60. Distance can be entered in kilometres (km) or miles (mi). Speeds can be entered in km/h or mph; both are converted to metric before the formula. Car default 170 g/km is mixed petrol; bike default 21 g/km is extra food energy, not zero. Times ignore lights and hills.
Distance: One-way length of the trip, in km or mi. A short commute is often 5–15 km.
Car g CO₂e / km: Grams of CO₂e per kilometre for the car. 170 is mixed petrol; a small EV on a green grid is much lower.
Bike g CO₂e / km: Grams of CO₂e per kilometre for the bike, mostly extra food. 21 is a common planning figure.
Car speed: Average car speed including traffic, in km/h or mph.
Bike speed: Average riding speed, in km/h or mph. A comfortable city pace is often 15–20 km/h.
Car / bike kg CO₂e: Carbon for that one-way trip.
Saved kg: Car minus bike.
Car / bike minutes: Time at the entered average speeds.
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