Ironman Nutrition Plan Calculator

Calculate hourly calorie, carb, sodium, and fluid intake targets for Ironman and long-course triathlon racing.

Inputs

Body weight (kg)

Expected race time (hours)

Heat Conditions

Sweat Rate

Tab to move between fields

Results

Bike calories/hr

223

Run calories/hr145

Bike carbs/hr (g)56

Run carbs/hr (g)36

Sodium/hr (mg)850

Fluid/hr (mL)850

Total race calories2,027

Total race carbs (g)507

Total sodium (mg)8,976

Total fluid (L)9

Gel equivalents20

Swim Hours1.2

Transition Hours0.24

How to Use This Calculator

Enter your Body Weight in kilograms.
Set your Expected Race Time in hours.
Choose Heat Conditions (Cool, Moderate, or Hot) and your Sweat Rate.
Review Bike Calories/Hour, Run Calories/Hour, Carbs/Hour, Sodium/Hour, and Fluid/Hour targets.
Use Total Race Calories, Total Carbs, Total Sodium, and Gel Equivalents to fill your special needs bags and aid station strategy.

How the result changes with Body weight (kg)

Body weight (kg)	Bike calories/hr
51	152
79	235
112	333
139	414

What each input means

Body weight (kg): Your body weight in kilograms. Used to estimate calorie expenditure and absorption rates.
Expected race time (hours): Estimated total race time in hours. Ironman finishes typically range from 8 to 17 hours.
Heat Conditions: Expected race day temperature. Affects sodium and fluid needs.
Sweat Rate: Your personal sweat rate. Affects sodium and fluid recommendations.

What each result means

Bike calories/hr: Target calorie intake per hour on the bike leg.
Run calories/hr: Target calorie intake per hour on the run (reduced due to GI stress).
Bike carbs/hr (g): Target carbohydrate grams per hour on the bike.
Run carbs/hr (g): Target carbohydrate grams per hour on the run.
Sodium/hr (mg): Target sodium intake per hour in milligrams.
Fluid/hr (mL): Target fluid intake per hour in milliliters.
Total race calories: Total calories needed across the entire bike and run.
Total race carbs (g): Total grams of carbohydrates needed for the race.
Total sodium (mg): Total sodium needed across the race.
Total fluid (L): Total fluid needed in liters.
Gel equivalents: Approximate number of energy gels (~100cal each) equivalent to total calorie needs.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Body weight (kg) = 75, Expected race time (hours) = 12, Heat Conditions = 2, Sweat Rate = 2 = 4 input(s) provided
Calculate Bike calories/hr
Bike calories/hr = round(calBurnPerHr * absorptionRate)
223 = 223
Calculate Run calories/hr
Run calories/hr = round(bikeCalPerHr * 0.65)
145 = 145
Calculate Bike carbs/hr
Bike carbs/hr = round(bikeCalPerHr / 4)
56 = 56

Engine last updated July 28, 2026.

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