The short answer
Eat a familiar carbohydrate-rich meal 1 to 4 hours before the start (1 to 4 g of carbohydrate per kg of body mass), then take in carbohydrate and fluid on the bike and the run. Sports nutrition guidance is roughly 30 to 60 g of carbohydrate per hour for about an hour or more, about 60 g per hour for races of 2 to 3 hours, and up to about 90 g per hour for ultra-endurance efforts. Drink enough to keep body mass loss under about 2 percent.
Before the start
Sports nutrition guidance (Burke et al., 2011) recommends 1 to 4 g of carbohydrate per kg of body mass in the 1 to 4 hours before exercise longer than an hour. For a 70 kg athlete that is 70 to 280 g. Choose food you have already tolerated in training, low in fat and fibre, and see race morning, hour by hour for where breakfast sits in the timeline.
For the days before a Half or a Full, the carb loading calculator turns your body mass into daily targets.
Carbohydrate per hour, by race length
| Time on course | Carbohydrate during | Typical race |
|---|---|---|
| Under about 1 hour | Not necessary; a mouth rinse or small amounts may help | Super Sprint, fast Sprint |
| About 1 hour and up | 30 to 60 g per hour (ACSM guidance) | Sprint, Olympic |
| 2 to 3 hours | Up to about 60 g per hour from a single carbohydrate source | Slow Olympic, fast Half |
| Long ultra-endurance efforts | Up to about 90 g per hour, from multiple transportable carbohydrates | Slow Half, Full |
These are Jeukendrup's 2014 review figures, and he notes they apply to most athletes but depend on the type and duration of activity. Which row you fall in depends on your time, so check the finish times by distance. Most of your carbohydrate belongs on the bike, where you can eat and drink easily; on the run you take what your stomach allows. The triathlon nutrition calculator gives a plan by distance and time.
Gels typically hold about 20 to 25 g of carbohydrate each, though brands differ (an estimate; read the label). So 60 g per hour is roughly 2 to 3 gels, and the gel calculator counts them for your race. Above about 60 g per hour the research calls for a mix of glucose and fructose, which the carb mix calculator helps build.
Fluid and sodium
The ACSM position stand on exercise and fluid replacement aims to keep water loss under 2 percent of body weight and to avoid large shifts in electrolytes. It recommends a drinking plan tailored to you, because sweat rates and sweat sodium vary widely between people, and it suggests measuring your own sweat rate from body weight before and after exercise. The sweat rate calculator does the arithmetic. A sports drink with carbohydrate and sodium works better than plain water over long efforts, and a commonly quoted figure for the sodium in drinks during long exercise is 0.5 to 0.7 g per litre.
Heat raises the numbers, cold lowers them. Do not copy someone else's bottle count: test yours on a long ride in conditions like race day.
First-timer mistakes
- Trying new gels, drinks or bars on race day. Practise your whole plan in a long training session or a brick.
- Waiting until you feel hungry or thirsty. On the bike, start within the first 15 to 20 minutes and then eat and drink on a timer (an estimate).
- Taking everything at once. Small, frequent amounts are easier on the stomach than a gel and a bottle together.
- Forgetting the run. Pack what you will carry or confirm where the aid stations are in the athlete guide, and add it to the packing list.
- Caffeine without testing it. See the caffeine calculator and use only an amount you already know.
Sources
- Jeukendrup A. A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Med 2014;44 Suppl 1:S25-S33
- Sawka et al., American College of Sports Medicine position stand: Exercise and fluid replacement. Med Sci Sports Exerc 2007;39(2):377-390
- Burke LM, Hawley JA, Wong SHS, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci 2011;29 Suppl 1:S17-S27 (1 to 4 g/kg carbohydrate 1 to 4 h before exercise; we read it in the GSSI review, not in the paper itself)
- Gel size, start timing and the 0.5 to 0.7 g/L sodium figure (quoted from the ACSM stand via a secondary source) are estimates; check labels and your own sweat test
Published 2026-10-20. Your race's athlete guide always has the final word on its rules and times.
Questions
What should I eat the morning of a triathlon?
A familiar, carbohydrate-rich meal 1 to 4 hours before the start, with 1 to 4 g of carbohydrate per kg of body mass, low in fat and fibre. Oats, white bread with jam, rice or a banana all work.
How many carbs per hour do I need in a triathlon?
About 30 to 60 g per hour for races of around an hour or more, up to about 60 g per hour for 2 to 3 hours, and up to about 90 g per hour in the longest races, using a mix of glucose and fructose above 60 g.
How much should I drink during a triathlon?
Enough to keep body mass loss under about 2 percent, which varies by person. Measure your sweat rate in training by weighing yourself before and after a session and adjust for heat.
Do I need gels for a Sprint triathlon?
Usually not. For a race under about an hour, carbohydrate during the race is not necessary, so a good breakfast and some water are enough. Longer races benefit from carbohydrate on the bike.
Should I use gels or sports drink?
Either works. Gels are compact and exact, drink provides fluid and carbohydrate together, and many athletes use both. Practise the combination in training, because stomach tolerance is personal.