Marathon Fueling Calculator
Marathon Fueling Calculator
Estimate carbohydrates per hour, gels needed, hydration and sodium for your marathon race plan.
Marathon Fueling Calculator
Estimate race-day carbs, gels, fluids and sodium
Use this as a planning starting point, then test your targets during long runs before race day.
Carbs/hour
75 g
Gels needed
12
Hydration/hour
500 ml
Sodium/hour
275 mg
Full-race estimate
- Total carbs
- 300 g
- Total fluid
- 1.95 L
- Total sodium
- 1100 mg
- Conditions
- Comfortable race conditions
Gel schedule
Take 1 gel about every 20 minutes.
Drink schedule
- Frequency
- Every 15 min
- Drink amount
- 125 ml
- Sodium
- 75 mg
How to use this
- Start fueling early, then spread gels across the race.
- Practice your target carbs/hour before race day.
- Treat fluid and sodium as estimates unless you know your sweat rate.
How marathon fueling estimates work
Marathon fueling depends on race duration, intensity, gut tolerance, sweat rate and race-day conditions. Most runners should treat the calculator as a starting point rather than a fixed rule.
Practice your target carbohydrate, fluid and sodium intake during long runs so your stomach, pacing and fueling plan are familiar before race day.
Related Marathon Tools
Frequently asked questions
How many carbs per hour should I take during a marathon?
Many marathoners aim for roughly 60-90 grams of carbohydrate per hour, but gut tolerance and race duration matter.
How often should I take gels in a marathon?
Most runners spread gels evenly from early in the race, often every 25-40 minutes depending on gel size and carb target.
Do I need sodium during a marathon?
Sodium can help replace sweat losses, especially in warm conditions or for heavy sweaters. Use the calculator estimate as a starting point.
Should I test my fueling plan before race day?
Yes. Practice your gel, drink and sodium schedule during long runs so your stomach is used to the plan.