Calculate Your Marathon

Carbohydrate Needs

Enter your body weight and goal finish time to get personalized race week fueling targets based on current sports nutrition guidelines.

Format: h:mm — e.g. 3:45 or 4:30

These recommendations are based on publicly available research and should not be taken as medical advice. If you have GI-specific sensitivities or other health concerns, consult a registered sports dietitian before race week.

Section 1

The day before the race

Carbohydrate loading target based on 6–12 g per kg of body weight.

— – — grams of carbohydrates
Stick to easy-to-digest sources — pasta, white rice, bread, bananas, and sports drinks. Cut back on fiber, fat, and protein, especially at dinner.

Sample day-before meal plan

Scaled to approximately — g — within your personal range.

Plan total — carbs

To hit the upper end of your range, increase pasta portions by 1–2 cups per meal or add another sports drink.

Section 2

Race day

Pre-race fueling

Choose one

Tap the window that fits your race morning schedule. Only eat one of these meals — not all three.

3 hours before the start — g
2 hours before the start — g
1 hour before the start — g

During the race

Start fueling 30–45 minutes in. Don't wait until you feel tired.

Per hour

60–90 g

Total estimate (—)

—–— g

To hit 90 g/hr you need to mix carb sources — glucose and fructose together. Think: a gel plus a sports drink, or chews plus a banana. Practice this combination on your long runs before race day.

How many gels to pack

Select the gel you plan to race with — or one with the same carbohydrate content. Your PDF will show only your selected gel. Based on your — finish time, 60–90 g/hr, includes one spare.

Gel Carbs Per hour Pack

Gel carb values sourced from manufacturer nutrition labels. Always test your race-day fuel in training.

Recommendations based on published sports nutrition guidelines (6–12 g/kg carbohydrate loading; 60–90 g/hr during endurance exercise). Individual needs vary — if you have GI sensitivities or specific health concerns, consult a registered sports dietitian before race week.

Sources

  1. Aktitiz, S., Kuru, D., Ergün, Z., & Turnagöl, H. (2024). Nutritional strategies for single and multi-stage ultra-marathon training and racing: from theory to practice. Turkish Journal of Sports Medicine. https://doi.org/10.47447/tjsm.0807.

  2. Kinrade, E., & Galloway, S. (2021). Dietary Observations of Ultra-Endurance Runners in Preparation for and During a Continuous 24-h Event. Frontiers in Physiology, 12. https://doi.org/10.3389/fphys.2021.765888.