Cycling nutrition calculator

The energy a ride costs comes straight out of the power: average watts multiplied by the seconds you rode gives kilojoules of mechanical work. A cyclist converts food to pedalling at roughly 22–25% efficiency, which means you burn about four times the work you produce — and because a kilojoule is about a quarter of a kilocalorie, kilojoules of work land within a few percent of kilocalories burned. The two errors cancel. It is the tidiest accident in sports science.

So a 700 kJ ride cost you roughly 700 kcal. No heart-rate estimate comes close to that accuracy.

Widely used general ranges, by ride length:

Above roughly 60 g an hour you need both glucose and fructose, because they are absorbed through different doors and one door alone jams. That is the whole trick behind the expensive gels.

Your gut has to be trained for this like anything else. Going from 30 g to 90 g an hour on the day of a long ride is how people end up walking to a hedge.

The 500–1000 ml an hour above is a starting point, not a prescription — real sweat rates run from 400 ml to over two litres an hour depending on heat, humidity and the individual. Indoors with no airflow sits at the top of that range, which is why a fan is the best value accessory in cycling.

Measure your own once: weigh yourself naked before and after a hard hour without drinking. Each kilogram lost is about a litre of sweat. One measurement tells you more than any calculator.

Everything above is the standard high-carbohydrate approach, and it is general information rather than advice for any particular person. If you eat low-carb or ketogenic, none of the carbohydrate figures apply to you — a fat-adapted rider running on 20 g an hour is doing something different, deliberately, and this page is not the place to argue about it.

Anyone managing a medical condition that involves blood sugar should take fuelling advice from someone who knows their case, not from a calculator on a stranger's website.