Cycling Calories: A Cleaner Number Than Most Wearables Give You

Most people learn the formula once in school and never touch it again — until life forces them to. Wearable cycling estimates vary 30%+. Power meters are the only honest answer.

The math

1 kJ of work ≈ 1 kcal burned (humans are ~24% efficient, and 1 kJ × 4 efficiency factor ≈ 1 kcal). Convenient coincidence.

Average rider

150W for an hour = 540 kJ ≈ 540 kcal. Doesn't depend on terrain — power tells truth.

Without a power meter

Heart-rate based estimates are 10–20% off; speed-based estimates often 30%+ off.

Pro tips

• Eat 60–90 g carbs/hour for rides over 90 minutes — bonking ruins the workout.
• Indoor trainers feel harder for same power — heat dissipation matters more than you think.

Frequently asked questions

Does drafting reduce calories burned? Significantly — 20–40% less effort at the same speed in a paceline.

Is cycling cardio or strength? Cardio with some leg endurance benefit. Add gym sessions for full strength.

Run your own numbers before you trust a rule of thumb. Two minutes saves a lot of regret.