Bike vs Car Carbon Footprint

What's the right comparison?

"How much CO₂ does cycling save vs driving" is a more subtle question than it looks. Four things that aren't usually in the calculation:

• Food is fuel. Cycling burns 25-50 kcal per km. Food production emits roughly 1.5-7 kg CO₂e per 1000 kcal depending on diet. We include this; most calculators don't.
• Bike manufacturing has an embodied cost. ~120 kg CO₂e per bike. Spread over 20,000 km that's 6 g/km — small but non-zero.
• Car and bus lifecycles. An ICE car produces ~200 g CO₂/km driving. A city bus produces ~80 g/km on average. An EV depends on the grid: ~50 g/km in clean grids, ~150 g/km in coal-heavy grids.
• Train is usually the cleanest motorized option. ~30-40 g/km even on mixed grids, because trains are so efficient.

What this calculator does differently

• Diet-aware food emissions. A vegan cyclist spends less CO₂ per km of riding than a meat-heavy one — by a factor of ~3.
• Grid-mix awareness. An EV in Norway and an EV in West Virginia are wildly different. We let you pick.
• Honest bus/train numbers. Per-passenger, with realistic load factors. A nearly empty bus is more polluting per passenger than a car.
• Embodied CO₂ amortized. Bike manufacturing isn't free; we include it as ~6 g/km so the comparison is honest.

What the numbers mean

Cycling wins decisively vs ICE cars and wins by a smaller margin vs EVs and transit. The interesting case is "should I drive the EV or ride the bike on a cold morning?" — the answer depends on how many calories you'll burn (cold air costs more energy) and what your grid mix is.

FAQ

Why is my bike number higher than "zero"?

Food has emissions. ~25 g/km is typical for a moderate-effort cyclist on an average diet. That's still 5-10× cleaner than driving.

What about bike vs e-bike?

E-bikes have higher manufacturing emissions (~150 kg CO₂e) but lower food emissions per km because the rider contributes less. On a coal-heavy grid, e-bike can still beat driving by 3×.

What about cargo bikes and kids?

Add ~50 kg for child + cargo, more food burned, but the comparison to driving a minivan widens further. Cargo bike vs SUV is one of the biggest carbon wins in personal transport.

What about the infrastructure?

Roads and rail have their own embodied emissions. This calculator focuses on the vehicle trip; full societal comparisons would include amortized infrastructure, which slightly favors cycling but not enough to change the conclusion.