Marathon Fueling Calculator
Calculate carbohydrate and electrolyte needs for marathon and long-distance races
About this calculator
The Marathon Fueling Calculator helps runners determine their optimal carbohydrate and electrolyte intake during long-distance races. Proper fueling is critical for maintaining energy levels, preventing hitting the wall, and optimizing marathon performance. This calculator takes into account your body weight, race duration, weather conditions, and sweat rate to provide personalized nutrition recommendations. By following these calculated guidelines, runners can avoid bonking, reduce cramping risk, and maintain steady energy throughout their 26.2-mile journey.
How to use
Enter your body weight, expected finish time, and race conditions (temperature, humidity). Input your estimated sweat rate if known, or use the calculator's default based on conditions. The tool will generate recommended carbohydrate intake per hour and electrolyte replacement needs, along with a fueling schedule for your race.
Frequently asked questions
How many carbohydrates should I consume per hour during a marathon?
Most runners need 30-60 grams of carbohydrates per hour, depending on body weight, pace, and individual tolerance levels.
When should I start fueling during my marathon?
Begin fueling within the first 45-60 minutes, before you feel hungry or low on energy, to maintain glycogen stores.
What electrolytes do I need during a long race?
Sodium is most important, typically 200-500mg per hour, along with potassium and magnesium to prevent cramping and dehydration.