Race Fuelling
Plan your endurance race fuelling strategy.Calculate carbohydrate intake, fluid needs, and sodium requirements per hour for Ironman, 70.3, marathon, and long endurance events.
Endurance fueling is rarely just about one variable. Race performance is influenced by how well athletes manage carbohydrate intake, fluid intake, and sodium replacement across the full duration of the event.
Because fueling needs change with event type, duration, conditions, gut training, and race intensity, a practical plan should be structured rather than improvised.
The Lytework Race Fueling Calculator helps endurance athletes estimate hourly carbohydrate, fluid, and sodium needs for Ironman, 70.3, marathon, and other long-course events.
Race Fueling Calculator
Estimate your carbohydrate, fluid, and sodium needs per hour for Ironman, 70.3, marathon, and long endurance events.
- Sets a practical carbohydrate target per hour.
- Builds an hourly fluid and sodium plan for the event.
- Converts sodium into Lytework capsules per hour.
- Shows total carbohydrate, fluid, sodium, and capsule requirements.
Select your event, enter details, and hit Build fueling plan to see your personalised protocol.
From numbers to race execution
Your fueling plan is only useful if it can be executed consistently.
Use your result as a starting point for:
- carbohydrate intake per hour
- fluid intake per hour
- sodium intake per hour
- total race-day requirements
Race fueling should always be tested in training before race day.
Reference ranges
Example race fueling scenarios
These are practical starting points only. Actual race fueling needs vary based on duration, conditions, gut tolerance, and athlete physiology.
| Event | Carbohydrates | Fluid | Sodium |
|---|---|---|---|
| MarathonRun-focused fueling plan | 45–75 g/hr | 400–800 mL/hr | 400–800 mg/hr |
| 70.3Middle-distance fueling plan | 60–90 g/hr | 500–900 mL/hr | 500–1000 mg/hr |
| IronmanLong-course fueling plan | 70–100 g/hr | 600–1000+ mL/hr | 700–1500+ mg/hr |
How to use this plan in training and racing
Most athletes do better with repeatable fueling than with aggressive but inconsistent intake.
A practical race fueling strategy usually means:
- starting early rather than waiting until late
- breaking intake into smaller repeated doses
- matching fluid intake to conditions
- separating sodium replacement from carbohydrate intake when more precision is needed
- testing the plan in long training sessions before race day
For longer events such as Ironman and 70.3, consistency often matters more than trying to “catch up” later.
Carbohydrate needs vary depending on event duration, intensity, and gut training. Many endurance athletes consume somewhere between 45 g and 100 g of carbohydrate per hour, with higher intakes usually requiring practice in training.
Fluid needs vary widely based on sweat rate, temperature, intensity, and event duration. Many athletes fall somewhere between 400 mL and 1000 mL per hour, although some may need more in hot conditions.
Sodium needs vary significantly between athletes because sweat sodium concentration and sweat rate differ widely. Some athletes may need only a few hundred milligrams per hour, while others may need more than 1000 mg per hour during long endurance events.
Yes. This race fueling calculator can be used to estimate carbohydrate, fluid, and sodium needs for Ironman racing. Because Ironman fueling is highly individual, athletes should use the calculator as a starting point and refine the plan through training.
Yes. 70.3 racing typically requires a structured fueling approach that balances carbohydrate, fluid, and sodium intake without overcomplicating execution. This calculator helps create a practical hourly plan.
Yes. Marathon fueling often requires a simpler and more tolerable plan than longer bike-based events. This calculator can help runners estimate a practical carbohydrate, fluid, and sodium strategy based on race duration and conditions.
Yes. Athletes who have trained their gut to tolerate more carbohydrate can often handle higher carbohydrate intake per hour. Athletes with less gut training may need a more conservative starting point.
Yes. GI sensitivity can affect the type and amount of fuel an athlete can tolerate during racing. Athletes with higher GI sensitivity often benefit from more conservative carbohydrate targets and well-practised fueling formats.