Endurance Sports Nutrition Calculator

Plan your nutrition strategy for marathons, triathlons, cycling events and other endurance activities

Fuel Your Performance

Proper nutrition is the foundation of endurance performance. Whether you're training for a marathon, preparing for a century ride, or competing in a triathlon, understanding your body's nutritional needs is critical for success.

Our comprehensive calculator helps you determine your personalized nutrition requirements based on your body metrics, training load, and event duration.

Pro Tip

For most endurance activities lasting over 90 minutes, athletes should aim to consume 30-60g of carbohydrates per hour to maintain performance.

Why Nutrition Planning Matters

Prevents Bonking 90%
Improves Recovery 85%
Enhances Performance 95%
Reduces GI Issues 75%

Nutrition Calculator

Enter your details to get personalized nutrition recommendations

Related Tools:

Pre-Workout Nutrition Calculator

Calculate optimal pre-workout nutrient timing and amounts.

Post-Workout Nutrition Calculator

Determine ideal recovery nutrition based on workout type.

Athlete Protein Needs Calculator

Calculate protein requirements for different sports and training intensities.

Strength Training Nutrition Calculator

Calculate macros for optimal muscle growth and strength gains.

Sports Hydration Calculator

Determine fluid needs based on exercise duration, intensity, and climate.

Carb-Loading Calculator

Plan carbohydrate intake before endurance events.

Race Day Nutrition Planner

Create hour-by-hour nutrition plan for race day.

Recovery Nutrition Calculator

Calculate optimal post-exercise nutrition timing and composition.

Muscle Building Nutrition Calculator

Determine calories and macros needed for muscle hypertrophy.

The Science of Endurance Nutrition

Energy Systems

During endurance exercise, your body relies on three primary energy systems:

1. Phosphagen System

Powers intense bursts lasting up to 10 seconds (sprints, high-intensity intervals).

2. Glycolytic System

Fuels efforts from 30 seconds to 3 minutes by breaking down glucose (middle-distance efforts).

3. Aerobic System

Primary system for endurance activities, using both carbohydrates and fats as fuel sources in the presence of oxygen.

Substrate Utilization

As exercise intensity increases, reliance on carbohydrates increases:

% Carbohydrate Use ≈ 0.01 × (% VO2max)² - 0.4 × (% VO2max) + 33

Carbohydrate Loading

Carbohydrate loading increases muscle glycogen stores by up to 100%, extending endurance performance capacity.

Traditional Protocol (3-Day)

Carbohydrate intake per day:

Carbohydrate (g) = Body Weight (kg) × 8-12g

For a 70kg athlete: 560-840g carbohydrates daily

Rapid Loading Protocol (1-Day)

Short, high-intensity exercise followed by:

Carbohydrate (g) = Body Weight (kg) × 10-12g

For a 70kg athlete: 700-840g carbohydrates in 24 hours

Important Note

Each gram of stored glycogen binds approximately 3g of water, so expect weight gain of 1-2kg during carb loading.

Hydration Science

Dehydration significantly impacts performance, with a fluid loss of just 2% body weight reducing performance by approximately 10-20%.

Sweat Rate Calculation

To determine your personal sweat rate:

Sweat Rate (L/hr) = [Pre-Exercise Weight (kg) - Post-Exercise Weight (kg) + Fluid Intake (L) - Urine Output (L)] ÷ Exercise Duration (hours)

Hydration Guidelines

General recommendations:

Hourly Fluid Intake: 400-800ml/hour
Sodium Intake: 500-700mg/L of fluid

Adjust upward in hot conditions or if you're a heavy sweater

Calorie Calculation

Understanding energy expenditure helps determine fueling requirements for endurance activities.

Metabolic Equivalent of Task (MET)

Energy expenditure based on activity intensity:

Calories Burned = MET × Weight (kg) × Duration (hours) × 1.0 kcal/(kg × hour)

Where MET values:
- Low intensity: 4-6 METs
- Moderate intensity: 7-10 METs
- High intensity: 11-15 METs
- Very high intensity: 16-20 METs

Performance Tip

For events lasting >90 minutes, aim to consume 30-60g of carbohydrates per hour to maintain performance.

Nutrition Strategies by Event Type

Marathon

  • Days Before: 8-10g carbs/kg body weight
  • Pre-Race: 2-3g carbs/kg, 3-4 hours before
  • During: 30-60g carbs/hour, 400-800ml fluid/hour
  • Hydration: Electrolyte drinks with 500-700mg sodium/liter
  • Format: Energy gels, chews, sports drinks

Key timing: Take carbs every 30-45 minutes starting at 45-60 minutes into the race

Century Ride

  • Days Before: 8-12g carbs/kg body weight
  • Pre-Ride: 1-4g carbs/kg, 1-4 hours before
  • During: 60-90g carbs/hour, 500-1000ml fluid/hour
  • Hydration: Electrolyte drinks with 700-1000mg sodium/liter
  • Format: Mix of solid foods and sports nutrition

Key strategy: Multiple carbohydrate sources (glucose + fructose) to maximize absorption

Triathlon

  • Days Before: 10-12g carbs/kg body weight
  • Pre-Race: 2-3g carbs/kg, 2-3 hours before
  • Swim: No intake (pre-load nutrition)
  • Bike: 60-90g carbs/hour, 500-750ml fluid/hour
  • Run: 30-60g carbs/hour, 400-600ml fluid/hour

Transitions: Use highly concentrated sources (gels) to quickly top up before the next segment

Key Features

Personalized Calculations

Get nutrition recommendations based on your specific metrics and activity.

Visual Analytics

View your nutrition needs represented in clear, interactive charts.

Science-Based

All calculations derived from sports nutrition research and studies.

PDF Export

Save your nutrition plan as a PDF reference for training and events.