Marathon Fuel Calculator
Plan your carbohydrate gel and hydration schedules for your marathon. Calculate total grams of carbs, electrolyte counts, and gel timings to fuel your muscles.
Configure Your Marathon Fuel Schedule
Input your target finish time, body weight, and nutrition options to create a personalized fueling plan.
Related Blog Guides
The Physiology of Glycogen Depletion and Fatigue
The human body can store roughly 400 to 500 grams of glycogen in the skeletal muscles and liver, which provides energy for approximately 90 to 120 minutes of high-intensity running. Once these reserves are exhausted, the body must switch to fat oxidation, which is a slower and less oxygen-efficient energy pathway. This sudden decrease in ATP production is known as "hitting the wall." Supplemental carbohydrate feeding during the race spares liver glycogen and sustains blood glucose levels, allowing muscles to maintain high rates of glycolytic metabolism.
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Running Pace Calculator
Calculate your running pace, speed and projected race finish times.
Running Split Calculator
Generate kilometer or mile pacing splits for target race times with customizable pacing models.
Water Intake Calculator
Calculate how much water you should drink each day.
Calories Burned by Heart Rate Calculator
Estimate calories burned during cardiovascular workouts using average heart rate and duration.
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Frequently Asked Questions
Disclaimer: Fuel absorption rates vary widely. Hydration and gastric tolerance are affected by heat, sweat rate, and gastrointestinal sensitivities. Full disclaimer →