NUTRITION & HYDRATION LAB
Energy Gel, Hydration & Electrolyte Calculator
Build a customized, science-backed race fueling plan for 10K, Half Marathon, Full Marathon, or Ultra distances. Keep your energy reserves high and banish the dreaded "hitting the wall" (bonking).
Race Fueling & Hydration Calculator (Energy Gel & Water Plan)
Accurately calculate your Carbs, Hydration, and Electrolyte requirements for race day.
⏱️ Race Fueling Timeline by Distance
Always chase your Gel with 100-150ml of plain water at aid stations. Avoid drinking sweet electrolyte fluids immediately after gels to prevent gut overload.
Carbohydrate & Fluid Intake Guidelines (ACSM Standards)
Recommended fueling rates and hydration targets for distance runners:
| Distance | Finish Time | Carb Intake (g/hr) | Estimated Gels | Hydration & Electrolytes |
|---|---|---|---|---|
| 5K - 10K | Under 60 min | 0 - 20g (Optional) | 0 - 1 gel (pre-race) | 150 - 300ml water |
| 21.1 km (HM) | 1h30 - 2h30 | 30g - 60g / hr | 2 - 4 gels | 400 - 600ml/hr + 1-2 salt tabs |
| 42.2 km (FM) | 3h00 - 5h30 | 60g - 90g / hr | 5 - 8 gels | 500 - 800ml/hr + 1 salt tab/hr |
| Ultra Marathon | Over 6 hours | 60g - 90g + solid food | Gels + energy chews/bars | Continuous electrolyte fluid intake |
Frequently Asked Questions About Marathon Fueling
Expert insights to help train your stomach and optimize gut absorption on race day.
How often should you take an energy gel during a Half or Full Marathon?
On average, consume 1 energy gel (containing 20g–30g of carbohydrates) every 35 to 45 minutes of running. For a Half Marathon, you generally need 2–3 gels. For a Full Marathon, budget between 5–7 gels depending on your target finish time.
Why should you always drink plain water when swallowing an energy gel?
Energy gels are hypertonic (high sugar concentration). Consuming them without water forces your stomach to draw fluid from your bloodstream to dilute the gel, often leading to nausea, cramping, and GI distress. Always chase your gel with 100–150ml of plain water at aid stations.
When do runners need electrolyte and salt supplements?
In hot or humid conditions, or during continuous runs lasting longer than 60 minutes, heavy sweat loss depletes sodium reserves. Taking 1 electrolyte salt tablet every 45–60 minutes helps prevent hyponatremia and cramping.