Get a gel-by-gel fueling plan for your race, personalized to your body and pace.
Most marathon runners need between 5 and 10 gels depending on their pace, gel size, and carb target. Faster runners (sub-3:30) may need fewer gels over less time, while runners finishing in 4+ hours need sustained fueling. Our calculator factors in your exact pace, gel product, and body metrics to give you a precise count.
For a marathon, take your first gel around 20–30 minutes into the race — before you feel like you need it. Starting early maintains glycogen stores and prevents the energy crash that comes from playing catch-up later. Our plan aligns your first gel to the nearest aid station so you can wash it down with water.
A general guideline is 400–800 ml per hour, but your actual needs depend on the weather, your sweat rate, and body weight. Our calculator personalizes your hydration target and pairs water intake with each gel at on-course aid stations, so you know exactly how many cups to grab.
Aim for 1.5–2.0 g of carbs per kg of body weight, 2–4 hours before the start. For a 70 kg runner, that's about 105–140 g of carbs — roughly 3 slices of toast with jam and a banana. Keep it low in fat and fiber to avoid GI distress. Our calculator gives you a personalized breakfast carb target based on your weight and expected race duration.