Marathon Fueling Calculator
Plan your carbohydrate and hydration strategy for race day.
About Race Fueling
Proper fueling is critical for marathons and half marathons. The body can only store ~90 minutes of glycogen at race pace.
Current guidelines: Most research supports 60-90g of carbs per hour for events over 90 minutes. Well-trained athletes may tolerate up to 120g/hr with mixed carb sources.
Timing your gels: Start fueling early (around 45-60 minutes in) before you feel depleted. Don't wait until you bonk.
Carb targets by race time:
30-60g/hrHalf marathon and shorter events
60-90g/hrMarathon (standard recommendation)
90-120g/hrMarathon+ (trained gut, mixed carbs)
120g+/hrUltra-endurance (highly individual)
Plan your race nutrition
Sign up for Hashiri.AI to set race goals and get personalized coaching.
Get Started Free