Race fueling planner: estimate carbohydrate by hour

What this tool calculates

Enter the planned exercise duration and the carbohydrate grams in one serving (gel, drink or food). The tool uses a 30–60 g/h planning range to estimate total carbohydrate, serving count and a rough distribution. Sessions under 60 minutes do not automatically add carbohydrate, so fueling does not become a task with no purpose.

The plan is a starting point, not a race-day prescription. Intensity, weather, gut tolerance and training habits all change what is practical at the same duration.

The 30–60 g/h range

The ISSN nutrient-timing position stand describes about 30–60 g of carbohydrate per hour for extended high-intensity exercise beyond 60 minutes, taken as a 6–8% carbohydrate-electrolyte solution every 10–15 minutes. That range is useful for planning, not a rule that everyone must reach the top end.

If a product label says something other than 25 g, enter the actual label value. Servings are rounded up so you carry enough; the distribution still needs adjustment in training. Higher intakes are not the tool's default recommendation, especially without practice.

Fluid is a separate plan

This tool estimates carbohydrate only, not fluid or sodium. Sweat rate varies with body size, weather, intensity, clothing and the individual; a fixed litre target easily misleads. Use the hydration guidance with thirst, urine colour, pre/post-run weight change and aid-station spacing.

Do not try a new gel, drink, salt tablet or concentrated formula for the first time on race day. Test it in training at similar intensity and duration, and record gut comfort and energy.

Using the result

Split the total across aid stations or carried servings, and set a simple reminder such as a small amount every 20–30 minutes; do not wait for obvious hunger or fatigue. For long or trail races, carry one extra portion and check whether you can carry enough fluid and food between stations.

If the plan causes bloating, nausea, frequent stops or energy swings, reduce concentration or portion size before changing products. Persistent gut problems deserve advice from a sports-nutrition or medical professional.

Tool limits

This tool does not provide an individual nutrition prescription, therapeutic diet, fluid target or medical clearance. People with diabetes, gastrointestinal disease, pregnancy, a history of disordered eating or medication use should discuss the plan with a clinician or registered dietitian.

Sources and scope

Carbohydrate ranges follow the ISSN nutrient-timing position stand; everyday and exercise hydration guidance follows the NHS. The tool uses a conservative 30–60 g/h planning range and does not cover every sport, climate or individual.

{
  "durationMinutes": 180,
  "productCarbsGrams": 30
}

{
  "durationHours": 3,
  "lowTotalGrams": 90,
  "highTotalGrams": 180,
  "servingsLow": 3,
  "servingsHigh": 6
}

{
  "durationMinutes": 90,
  "productCarbsGrams": 25
}

{
  "durationHours": 1.5,
  "lowTotalGrams": 45,
  "highTotalGrams": 90,
  "servingsLow": 2,
  "servingsHigh": 4
}