Carb and fuelling planner

How much carbohydrate to take for a session or race, how many gels and bottles to pack, and when to take them.

What are you doing?

Pick more than one for a brick, such as bike then run.

Bike time

hmin

How hard?

Your gut

Your gels, drink and weight (optional)

Carbs per gel (g)On the packet. Most gels have 20 to 40 g.Carbs per bottle of drink (g)0 if you only drink water.Bottle size (ml)Your weight (kg)For what to eat before. Shared with the tyre pressure tool.

Aim for

45 g carbs per hour

80 g in total: 2 bottles of drink mix (40 g in 500 ml).

Your fuelling schedule

0:15Bike: 200 ml drink mix (16 g)16 g
0:35Bike: 200 ml drink mix (16 g)32 g
0:55Bike: 200 ml drink mix (16 g)48 g
1:15Bike: 200 ml drink mix (16 g)64 g
1:35Bike: 200 ml drink mix (16 g)80 g

Times are from the start. The right-hand column is the running total of carbohydrate.

Drink: about 1 litres in total, roughly 500 ml an hour. Drink more in the heat, but not so much that you gain weight during the session.

Make it work on the day

Practise it in training. Your gut adapts: taking carbohydrate in at least one long session a week makes race-day fuelling easier to stomach. Never try a new gel or drink on race day.
Little and often. Small amounts every 20 minutes sit better than a lot at once. Start early, before you feel you need it.
Keep drinks at normal strength. Mix your drink as the packet says and take gels with it or with water. Very concentrated drinks are more likely to upset your stomach.
Running is harder on the stomach than cycling. In a triathlon, do most of your eating on the bike.
Hot day or salty sweat? Use a drink with electrolytes, especially in sessions over 2 hours.

How this is worked out

The amount per hour follows the 2016 joint position of the American College of Sports Medicine, the Academy of Nutrition and Dietetics and Dietitians of Canada: nothing needed under 45 minutes, small amounts up to 75 minutes, 30 to 60 g an hour up to 2.5 hours, and up to 90 g an hour beyond. Easy sessions sit at the bottom of each range and races at the top. Before the event: 1 to 4 g per kg of body weight 1 to 4 hours before, and carbohydrate loading of 10 to 12 g per kg a day for races over 90 minutes. Drink: 0.4 to 0.8 litres an hour.

Above about 60 g an hour your gut needs glucose and fructose together, and needs to be used to it, so we hold that level until you say your gut is trained. 90 g an hour is the current consensus ceiling: studies have shown 120 g an hour can be tolerated, but not yet that it makes you faster (Gatorade Sports Science Institute, 2022). In a study of Ironman athletes, those who took more carbohydrate finished faster, while marathon runners managed far less than cyclists (Pfeiffer and others, 2012), which is why the run is held to 60 g an hour unless your gut is trained.

Our own choices: where in each range to aim for easy, steady and race; a gel 15 minutes before a triathlon swim, when you cannot eat; feeding every 20 minutes from 15 minutes in; and drinking 400 to 600 ml an hour. These are a starting point. If you have a medical condition such as diabetes, ask your doctor or a sports dietitian.