Cycling Calorie Calculator

With a power meter, calorie burn is refreshingly simple. The mechanical work you do is average power × time, in kilojoules. Because human muscular efficiency is around 20–25%, a neat coincidence falls out: the kilojoules of work you produce are almost exactly equal to the kilocalories you burn.

So a ride that records 900 kJ of work burned roughly 900 kcal. Without a power meter this is only a rough estimate — power-based figures are far more accurate than speed-and-weight guesses.