Race Nutrition Calculator

How to use the Race Nutrition Calculator

Answer six questions. It takes about a minute, and there's no right answer to fake.

1. Distance. Sprint, Olympic, half or full. This sets your carbohydrate target more than anything else.
2. How hard you're racing. Racing the clock, solid mid-pack, or steady all day. This sets how long each leg takes and trims your carb target if you're going slower.
3. Body weight band. Used for fluid and caffeine. It doesn't change your carbs.
4. Sweat profile. Think about a hard two-hour session. If your kit dries with white salt marks, you're a heavy, salty sweater.
5. Race-day forecast. Cool, mild, or hot and humid. Check the forecast the week of the race and run it again if it changes.
6. Caffeine habit. None, a little, or "I train with it". This sets how much caffeine the plan includes.

You get four numbers: carbs, sodium and fluid per hour, plus a caffeine total for the race. Below them is a leg-by-leg plan with your estimated time for each leg, and, when our product data is verified, a shopping list of gels, drink mix and electrolytes that add up to the targets. If you don't get a shopping list, read the labels on what you already use: grams of carbohydrate and milligrams of sodium per serving are all you need.

If you've trained your gut to take more carbs, or less, use the slider to change your carbs per hour. The plan and quantities update as you move it. Then print the plan or save the link. Every answer is in the page address, so a bookmark brings back the same plan.

How to build your race fuelling

Fuel the bike and run, not the swim. You can't eat in the water, so the calculator only counts bike and run time when it works out your totals. Have a gel 10–15 minutes before the start so you begin topped up.

Carbs depend on the race, not your size. The calculator sets carbs by distance, then scales them down if you're racing at a steadier pace. A 60 kg (132 lb) athlete and a 90 kg (198 lb) athlete racing the same half at the same effort get the same target, about 80 g an hour at the fast end. Olympic tops out at 60 g an hour, full distance at 85 g, and a sprint sits at 25–30 g. Hot conditions trim the target slightly. The plan never goes below 25 g an hour.

Sodium depends on you, not the distance. It starts from your sweat profile and goes up or down with the forecast. A light sweater on a cool day gets around 300 mg an hour. A heavy, salty sweater in the heat gets well over 1,000 mg. The calculator adds up the sodium your gels and drink mix already carry, and only adds an electrolyte product if there's still a meaningful gap. It never adds one for a sprint, because you're done before a deficit matters.

Fluid depends on sweat, heat and body size. Your sweat profile sets the baseline, the forecast scales it, and heavier athletes get proportionally more. It's capped at 1,200 ml (about 40 fl oz) an hour, because past that most people are carrying fluid, not absorbing it. If you hit the cap, drink to thirst on top of it and take the sodium seriously.

Caffeine depends on your habit and weight. "A little" gives you 1.5 mg per kg of body weight for the race, "I train with it" gives 3 mg per kg, rounded and capped at 400 mg. "None" gives none, and the plan won't push you to start on race day. In the shopping list, caffeinated gels replace plain ones instead of adding to them. Take them in the last third of the race, when effort is high and the caffeine will still be working.

Most of the eating happens on the bike. It's the leg where you can carry bottles and your stomach is most cooperative. The plan fills your bottles with drink mix up to what you'd actually drink, then makes up the remaining bike carbs with gels. On the run it's gels plus whatever the aid stations hand out.

Then practice it. Do at least two long sessions on exactly this plan before race day, especially if your target is 80 g an hour or more. Your gut is trainable, but only in training.

If you have diabetes, a heart condition, kidney problems, a history of hyponatremia, are pregnant, or take medication that affects fluid or caffeine, see your doctor or a sports dietitian before using these numbers. This is general fueling guidance, not medical advice.

Common mistakes

• Trying something new on race day. A new gel, a new mix, or a carb rate your gut hasn't seen. If it isn't in your long sessions, it isn't in your race.
• Leaving it all for the run. By then you're behind and your stomach is bouncing. Front-load on the bike.
• Drinking water and calling it hydration. On a hot, long day, lots of fluid without sodium can leave you worse off. Hit both numbers.
• Taking caffeine at the start. It's mostly gone by the time you need it, and it can make a nervous stomach worse.
• Buying exactly what the plan says. Gels get dropped. Buy a spare of everything and add it all to your race-day gear checklist.
• Using a forecast from three weeks out. Rerun the calculator in race week. Hot conditions change your sodium and fluid a lot.

FAQ

How many carbs per hour do I need for a half Ironman / 70.3?

The calculator gives between 65 g and 80 g an hour for a half, depending on how hard you're racing and whether it's hot. Racing the clock in cool or mild conditions gets the top of that range.

Sports nutrition guidance commonly suggests up to about 60 g of carbohydrate an hour from a single sugar source, and up to about 90 g an hour from glucose-fructose mixes for events lasting longer than about 2.5 hours. Higher rates need gut training, so build up to them in training.

How much sodium do I need per hour in a triathlon?

The calculator gives about 300 mg to about 1,450 mg an hour, set by your sweat profile and the forecast. An average sweater on a mild day gets 700 mg.

Individual sweat varies a lot, so if your answer doesn't match how you feel in long sessions, adjust it in training. If you have high blood pressure or kidney problems, ask your doctor before adding salt.

How much should I drink per hour during a triathlon?

The calculator gives about 250 ml (8 fl oz) an hour for a light sweater in the cool up to a cap of 1,200 ml (about 40 fl oz) for heavy sweaters in the heat. Most people land somewhere between those.

Weighing yourself before and after a long training session, adjusting for what you drank, gives a rough estimate of your sweat rate. Drinking far more than you lose can dilute blood sodium (hyponatremia), which is dangerous, so don't force fluid beyond the plan and your thirst.

Should I use caffeine during a triathlon?

Only if you already use it in training. The calculator gives 1.5 mg per kg for a light habit and 3 mg per kg if you train with it, capped at 400 mg for the race. If you choose "None", it gives you none.

Take it in the back half of the race. If you have a heart condition, are pregnant, or take medication, check with your doctor before using caffeine in a race.

Do I need to eat during a sprint triathlon?

Not much. The calculator gives a sprint 25–30 g of carbs an hour across the bike and run, which often means one gel or a bottle of drink mix. It never adds an electrolyte supplement for a sprint.

A good breakfast and a gel before the start matter more at this distance than anything you take during the race.

Why doesn't my body weight change my carbs?

Because your carb target depends on the race. How fast you can absorb carbs during exercise doesn't scale neatly with body size, so the calculator sets carbs by distance and pace. Your weight still changes your fluid and caffeine numbers.