Carb Loading Calculator
Calculate how many carbs you need per day in the 3 days before your race. Based on sports nutrition research for endurance athletes.
Carb loading vs carb timing: this calculator covers pre-race loading (how many carbs per day in the 2-3 days before your race). If you need an on-race fuelling schedule (gels and carbs per hour during the event), use the Carb Timing Calculator instead.
How much should you carb load before a triathlon?
Aim for 8–12 g of carbs per kg of body weight per day in the final 48–72 hours before a 70.3 or Ironman. A 70 kg athlete needs roughly 560–840 g of carbs daily. That is a lot more food than most triathletes realise — the mistake is under-eating in the days before the race. Sprint and Olympic races need a lighter top-up, not full loading.
- Sprint (<1.5 h): normal diet + slight carb bump day before
- Olympic (2–3 h): 6–8 g/kg for 1 day pre-race
- 70.3 (4–7 h): 8–10 g/kg for 2 days pre-race
- Ironman (10+ h): 10–12 g/kg for 2–3 days pre-race
Your Details
Carb loading is most effective for races lasting 90+ minutes. For sprint triathlons, normal pre-race eating is usually sufficient.
Enter your details and click calculate to see your personalized carb loading plan.
Sample Carb Loading Meals
Hitting high carbs per day can be tough. Here are easy, gut-friendly options that pack in the carbs without excess fiber:
Breakfast (~100-120g carbs)
- • 2 cups white rice with honey
- • 1 banana + glass of orange juice
- • OR: 4 pancakes with maple syrup + fruit
Lunch (~100-120g carbs)
- • Large bowl of pasta with marinara
- • White bread roll + sports drink
- • OR: Large sub sandwich + pretzels
Dinner (~100-120g carbs)
- • Large serving of rice + lean protein
- • Baked potato + roll
- • OR: Sushi rice bowls
Snacks (~50-80g carbs each)
- • Sports drink (500ml = ~30-40g)
- • Energy bars or fig bars
- • Applesauce + crackers
Example calculation
Athlete: 70 kg triathlete prepping a full Ironman, moderate training volume.
Peak daily carbs: 70 × 12 = 840 g/day.
3-day taper: 630 g → 756 g → 840 g.
Per meal: ~170 g over 5 meals, or 120 g meals + 2 carb-heavy snacks.
Expect: 1–2 kg of glycogen water weight gain — this is normal and a sign loading worked.
Common mistakes
- Under-eating by 200+ g/day — most athletes think they loaded but came up short
- Adding fibre with the carbs — whole-grain bread and brown rice cause race-morning GI issues
- Panicking about the 1–2 kg scale bounce — that's bound water, not fat
- Starting the load too late — 24 hours is not enough for full-distance events
- Loading for a sprint — unnecessary, normal eating covers it
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How this calculator works
Daily carb target = body weight × g/kg target by distance (Burke 2011, Thomas 2016). 3-day taper: 75% / 90% / 100%.
Assumptions
- • 7–12 g carbs/kg/day depending on race distance
- • Activity level multiplier scales total calorie estimate
- • 5 meals/day for distribution
Limitations
- • Expect 1–2 kg of glycogen-bound water weight gain — normal
- • Not a long-term diet — load only 1–3 days pre-race
- • GI tolerance varies — practise loads in training first
Who this is for
- • Triathletes prepping a 70.3, Ironman or marathon
- • Athletes who feel flat in the final 90 minutes of long races
- • Anyone testing a load protocol in training before race day
Who this is not for
- • Athletes with diabetes or blood-sugar conditions
- • Sprint-distance racers — minimal load needed
Carb Loading FAQ
Scientific References
Guidelines for carbohydrate intake before and during endurance events
Comprehensive position statement on nutrition for athletes