A car commute is about 170 g of CO2 per kilometre; a bike is close to zero
The gap is the whole story. Multiply your round-trip distance by commuting days by the per-kilometre figure. For a 10 km each-way commute, 250 days a year, the car puts out roughly 850 kg of CO2 while the bike accounts for about 80 kg once food and manufacturing are included.
Same 20 km daily commute, 250 days: the bike cuts emissions by about 770 kg a year — roughly a 90% reduction.
Annual CO2 by commute distance
Round-trip distance, 250 commuting days, petrol car at 170 g/km against a regular bike at 16 g/km.
| One-way distance | Car | Bike | Saved per year |
|---|---|---|---|
| 3 km | 255 kg | 24 kg | 231 kg |
| 5 km | 425 kg | 40 kg | 385 kg |
| 10 km | 850 kg | 80 kg | 770 kg |
| 15 km | 1,275 kg | 120 kg | 1,155 kg |
| 20 km | 1,700 kg | 160 kg | 1,540 kg |
One mature tree absorbs about 20 kg of CO2 a year, so a 770 kg saving is roughly what 38 trees soak up over a year.
Where the numbers come from
- Car figure. A gallon of petrol releases about 8,887 g of CO2 (EPA); 170 g/km is the average for a typical passenger car. Diesel is higher, a hybrid lower, and an EV shifts emissions to the grid.
- Bike is not literally zero. The 16 g/km comes from the extra food you eat; add a few grams for building the bike over its life. An e-bike lands near 14 g/km including charging.
Common questions
How much CO2 does a car commute produce?
A typical petrol car emits about 170 grams of CO2 per kilometre from the tailpipe. A 20 km round-trip commute, 250 days a year, comes to roughly 850 kg of CO2, or 0.85 metric tons.
Is cycling really zero CO2?
The bike itself has no tailpipe emissions. Counting the extra food energy you burn plus the amortised cost of building the bike, cycling works out to roughly 15 to 21 grams of CO2 per kilometre, about a tenth of a car.
How much CO2 can I save by switching to a bike?
For a 20 km daily commute over 250 days, switching from a petrol car to a bike saves around 770 kg of CO2 a year, roughly a 90% cut. Multiply your own round-trip distance by days per year to scale it.
