Tell it how long and how hard you ride. You get the carbs per hour the sports nutrition guidelines recommend, turned into gels and bottles on a schedule, plus a sweat test, a plan to train your gut and what to eat before and after.
Trained 75 kg men riding without food, in a laboratory study (van Loon et al. 2001). Most of it comes from stored glycogen, so it is not a target for eating.
Weigh yourself naked before and after a ride of at least an hour, dry off first, and note everything you drank. Go to the toilet before you weigh in.
Product figures are from each maker's website. Check the label: recipes change.
The joint position of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada sets carbohydrate during exercise by how long it lasts. Under 45 minutes you do not need any. From 45 to 75 minutes, small amounts, or even rinsing a sports drink around your mouth, are enough. From 1 to 2.5 hours, 30 to 60 g per hour. Beyond 2.5 to 3 hours, up to 90 g per hour.
The calculator places you inside that band by how hard you ride: the low end for an easy ride, the middle for steady riding and the top for a race. Asker Jeukendrup, whose work the guidelines draw on, advises less when the intensity is low, and notes that these figures are for well-trained athletes.
Your body weight does not change the number. The limit is how fast your gut can absorb carbohydrate, not how big you are, so the advice is in grams per hour, not per kilo.
Glucose alone is absorbed and burned at about 1 g per minute, 60 g an hour, however much you take. Fructose uses a different route through the gut wall. In laboratory tests, glucose and fructose together were burned at 1.26 g per minute, and up to 1.75 g per minute at very high intakes.
It shows in performance: in one study, a glucose and fructose drink gave an 8% better time trial than glucose alone. Mixes with about 0.8 g of fructose for every gram of glucose were burned best and caused the fewest stomach problems. That is why the planner warns you if you aim above 60 g an hour with a product that has no fructose.
Riders with a trained gut can absorb it: at 120 g an hour of glucose and fructose, trained cyclists burned 1.5 to 1.7 g per minute of what they took. A 2026 review proposes raising the upper limit to 120 g for trained athletes.
What no trial has shown yet is that 120 g makes a cyclist faster than 90 g. In two studies, riders taking 90 g an hour of a 2:1 mix did better in a time trial than at 100 or 112.5 g. The calculator lets you choose 120 g only if you say your gut is trained, and only for rides over 2.5 hours.
In a laboratory study of trained 75 kg men riding without food, carbohydrate burned came to about 86 g an hour at 165 W, 122 g at 227 W and 235 g at 310 W. At race pace that is more than double what anyone can absorb.
The difference comes from the glycogen stored in your muscles and liver. Eating on the bike does not replace it all; it makes it last longer. Those figures are for one group of riders, so the calculator shows them as a reference, not as your number.
In a survey of 221 endurance athletes, 4% of cyclists in a race had serious stomach problems, against about 31% in an Ironman. Higher intakes went with more nausea, and the strongest link was a history of stomach problems.
The gut adapts. Cyclists who ate a high-carbohydrate diet for 28 days burned more of the carbohydrate they drank during exercise. Runners who practised taking 90 g an hour in 10 sessions over two weeks had 60% fewer gut symptoms. No study says how big each step should be: the ladder in the calculator adds 10 g an hour each week, which is our suggestion.
Sweat rates run from about 0.5 to 2 liters an hour, and each liter carries roughly 230 to 1,600 mg of sodium depending on the person. No guideline sets one sodium figure per hour. The American College of Sports Medicine advises drinking enough to lose no more than 2% of your body weight, and not so much that you gain weight.
The sweat test in the calculator tells you your own rate: weigh yourself before and after a ride, note what you drank, and it works out how much to drink on a longer ride to stay under 2%. The guidelines suggest adding sodium when you sweat more than 1.2 liters an hour, your sweat is salty or the ride is longer than 2 hours.
Before a ride of more than an hour, the guidelines suggest 1 to 4 g of carbohydrate per kilo of body weight in the 1 to 4 hours before. With less than 8 hours before your next hard session, 1 to 1.2 g per kilo each hour for the first 4 hours. Before an event of more than 90 minutes, carbohydrate loading means 10 to 12 g per kilo a day for 36 to 48 hours.
Day to day, the need follows training: 3 to 5 g per kilo on light days, 5 to 7 for about an hour a day, 6 to 10 for 1 to 3 hours and 8 to 12 above 4 to 5 hours.
It covers the ride and the hours around it. What you eat the rest of the week depends on your training load and your goals.
If you have diabetes, a digestive condition or a history of eating disorders, plan your fueling with a doctor or a sports dietitian.
Jeukendrup says so of his own version of the bands, and suggests adjusting down if you are newer to the sport. The gut setting in the calculator does that for you.
For rides of 1 to 2.5 hours, 30 to 60 g per hour; for longer rides, up to 90 g, from a mix of glucose and fructose. Under 45 minutes you do not need any. Take the lower end on easy rides and the upper end when racing.
It depends on the gel and what is in your bottle. At 60 g an hour, that is about three 22 g gels, or one 40 g gel with a bottle of a 36 to 40 g drink. The planner in the calculator works it out for the products you use.
Riders with a trained gut can absorb it, but no trial has shown that cyclists go faster with 120 g than with 90 g. In two studies, 90 g an hour gave a better time trial than 100 or 112.5 g.
Glucose on its own is absorbed at about 60 g an hour at most. Fructose uses a second route, so glucose and fructose together can be absorbed faster. Above 60 g an hour, use products that contain both.
No. During the ride the limit is how fast the gut absorbs carbohydrate, not body size, so the advice is in grams per hour for everyone. Body weight matters for the meals before and after.
Enough that you lose no more than 2% of your body weight over the ride, and not so much that you gain weight. Sweat rates range from about 0.5 to 2 liters an hour, so measure yours with the sweat test above.
There is no single figure: sweat carries roughly 230 to 1,600 mg of sodium per liter depending on the person. The guidelines suggest sodium when you sweat more than 1.2 liters an hour, your sweat is salty or the ride is longer than 2 hours.
Practise your race intake on long training rides. Studies trained the gut for 2 to 4 weeks. Start at what sits well and add a little each week; the calculator builds a ladder at 10 g an hour per week.
