Free half marathon nutrition tool
Half marathon fuel calculator
Create a half marathon fueling plan that estimates how many gels you need, when to take them, how much water to pair with fuel, and whether your target pace needs light or full race-day fueling.
Build your race fuel plan
Calculate a half marathon fueling plan from your target pace, gel product, carb target, body metrics, weather, and sweat profile. Connect a mapped race course if you want the plan aligned to real aid stations.
How to use this calculator
Start with the race distance, then personalize the plan around the fuel you actually use in training.
Choose half marathon as the race type, or connect a supported half marathon course.
Enter target pace, gel carbs, body metrics, heat, sweat rate, and sweat saltiness.
Generate the plan to see gel timing, total carbs, hydration, sodium, caffeine, and pre-race carb targets.
Fuel calculator FAQ
Quick answers for race-day carbs, gel timing, hydration, and distance-specific fueling decisions.
Do I need gels for a half marathon?
If your half marathon will take longer than about 60 minutes, taking carbs during the race can help maintain pace. Faster runners may only need one or two gels, while two-hour runners often benefit from more.
How many gels should I take in a half marathon?
Most runners use 1 to 4 gels in a half marathon. The right number depends on finish time, gel size, target carbs per hour, and how well you tolerate fuel at race pace.
When should I take my first half marathon gel?
A common starting point is 20 to 30 minutes into the race. If you expect to finish quickly, one early gel may be enough; longer finish times usually need a repeat intake later.