Last reviewed: April 2026
How Many Carbs Per Hour in a Triathlon?
Aim for 30g/hr for sprint, 60–75g/hr for Olympic, 75–90g/hr for 70.3, and 90–120g/hr for Ironman. Lower the ceiling if your gut isn't trained for it; raise it gradually with a 2:1 glucose-to-fructose ratio. The table below shows race duration, carbs per hour, and what that looks like in gels or drink mixes.
How many carbs per hour do you need in a triathlon?
- • Under 60 min: 0–30 g/hr — water usually covers it.
- • 1–2.5 hrs (sprint / fast Olympic): 30–60 g/hr from any carb source.
- • 2.5–5 hrs (Olympic / 70.3): 60–90 g/hr, mix glucose + fructose.
- • 5+ hrs (Ironman): 90–120 g/hr, requires gut training.
Carbs per hour by race duration
| Duration | Carbs / hr | In gels | In drink mix |
|---|---|---|---|
| Under 1 hr | 0–30 g | 1 optional | 1 bottle |
| 1–2.5 hrs | 30–60 g | 1–3 gels | 1–2 bottles |
| 2.5–5 hrs | 60–90 g | 3–4 gels + mix | 2–3 bottles |
| 5+ hrs | 90–120 g | 4–5 gels + bars + mix | 3+ bottles |
Assumes ~22 g carbs per standard gel and ~40 g carbs per 500 ml drink-mix bottle.
The 2:1 glucose-to-fructose rule
Your gut absorbs glucose and fructose via separate transporters. Using only glucose caps absorption at ~60 g/hr. Mixing 2 parts glucose to 1 part fructose unlocks 90–120 g/hr — which is why elite Ironman athletes can fuel at those rates without GI issues.
Products engineered for this include Maurten, SiS Beta Fuel, and Precision Hydration. Check the label for both "glucose / maltodextrin" and "fructose" in the ingredients.
How to train your gut
- Start at 30 g/hr in long sessions (2+ hours).
- Add 10 g/hr each week until you hit your race target.
- Rehearse race-day products at race-day timing on at least 3 sessions.
- If GI issues appear, drop by 20 g/hr and rebuild more slowly.
Personalised plan: Race Nutrition Planner.
Try a calculator
- Carb Mix Calculator
Get the glucose:fructose mix to safely hit 90g/hr.
- Carb Timing Calculator
Schedule gels across the bike and run.
- Race Nutrition Planner
Turn your per-hour target into a full race plan.