How many calories does cycling burn?
Between about 200 kcal an hour pedalling to the shops and over 1,000 at 40 km/h on the drops. That range is far wider than walking’s, and the reason is air.
Speed is almost the whole story
Walking costs roughly 0.5 kcal per kilogram of bodyweight per kilometre, and pace barely changes it — you are moving a given mass a given distance either way. Cycling does not work like that. The frame carries your weight, so on level ground you are not lifting anything. What you are fighting is drag.
Drag force rises with the square of your speed, which means the power needed to overcome it rises with the cube. Ride 25% faster and you need roughly double the watts. Above about 25 km/h (15.5 mph) aerodynamic drag is the majority of what you are working against; by 40 km/h (25 mph) rolling resistance is close to a rounding error.
| Speed | Power | Burn per hour | |
|---|---|---|---|
| 20 km/h | 12 mph | ~60 W | ~215 kcal |
| 25 km/h | 15.5 mph | ~95 W | ~340 kcal |
| 30 km/h | 18.5 mph | ~150 W | ~540 kcal |
| 35 km/h | 22 mph | ~220 W | ~790 kcal |
| 40 km/h | 25 mph | ~315 W | ~1,130 kcal |
Solo, flat, no wind, road bike, rider plus bike around 85 kg (187 lb). Doubling your speed from 20 to 40 km/h multiplies the burn by more than five. Nothing in walking behaves like this.
Note what is missing from that table: your bodyweight. On the flat it barely matters, because nothing is being lifted — a heavier rider pays only slightly more rolling resistance. This is the exact opposite of walking, where weight is the dominant variable.
Watts are the honest measure
A power meter measures force and velocity at the crank. That is a direct physical measurement of mechanical work, not an inference from your pulse — and it converts to energy with arithmetic rather than guesswork.
At a gross mechanical efficiency of around 24%, one watt held for an hour costs you roughly 3.6 kcal. So:
- 150 W for an hour → ~540 kcal
- 200 W for 90 minutes → 200 × 3.6 × 1.5 = ~1,080 kcal
There is an even quicker version. The kilojoules of work on your head unit are within a few percent of the kilocalories you burned, because dividing by ~24% efficiency and converting kJ to kcal very nearly cancel out. A 900 kJ ride cost you about 900 kcal. That coincidence is the most useful number in cycling.
It is also a gross figure — your resting burn is inside it, not on top of it. That distinction does more damage to people’s maths than any measurement error, and it is covered properly in what 10,000 steps actually burns.
Why a wrist estimate struggles on a bike specifically
Cycling is close to the worst case for a wrist tracker. Your hands sit still on the bars, so the motion channel contributes almost nothing and the device falls back on heart rate alone. Heart rate then drifts with heat, dehydration, caffeine and simple fatigue — on a long ride it climbs while your actual output falls.
Drafting breaks it completely. Sitting on a wheel cuts your drag by 25–30%, and deeper in a bunch by nearer 40%, so you hold the same 32 km/h on two-thirds of the power. Your heart rate drops accordingly, but the watch has no idea whether you are sheltering or on the front. More on where these estimates hold up in how accurate Apple Watch calorie tracking is.
Hills and the freewheel problem
Climbing switches the physics back to something like walking: you are lifting mass against gravity, and weight matters again. Hauling 85 kg (187 lb) of rider and bike up 300 m (1,000 ft) of ascent takes about 250 kJ of work — roughly 250 kcal — regardless of whether you crawl or attack it. The number is set by the hill, not the effort.
The descent is the mirror image, and it is why time in the saddle is a poor proxy for energy. Freewheeling costs you essentially nothing. A 90-minute ride through hilly terrain or town traffic can contain twenty minutes at genuinely zero watts: coasting, braking, waiting at lights. Two riders both logging “90 minutes” can differ by 400 kcal.
So which burns more, walking or cycling?
Both, depending on what you hold constant.
Per kilometre, walking wins easily. A 70 kg (155 lb) person walking 10 km (6.2 miles) burns around 350 kcal. Riding the same 10 km at 25 km/h takes 24 minutes at about 95 W — roughly 135 kcal. Cycling is around two and a half times cheaper per kilometre, which is rather the point of a bicycle.
Per hour, cycling wins. You cannot walk at 25 km/h. An hour’s brisk walk is about 175 kcal; an hour at a steady club pace is twice that or more.
If you are working out what to aim for across a week rather than a session, how many calories you should burn a day is the better frame, and a maintenance calorie estimate gives you the baseline those rides sit on top of.
The practical summary
Buy or borrow a power meter if you ride seriously; its kilojoule total is the most trustworthy energy figure available to any amateur athlete in any sport. Without one, estimate from average speed rather than time, and discount heavily for coasting, traffic and sitting in a group. Then remember you were going to burn something during that hour anyway.
General information, not medical advice.