Free race-day nutrition tool

Marathon fuel calculator

Build a marathon fueling plan that turns your pace, gel choice, body metrics, sweat profile, and weather into clear gel timing, carb targets, hydration, sodium, caffeine, and pre-race carb guidance.

Build your race fuel plan

Calculate a 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.

Race

Race

Choose the distance, connect a course if available, and set your expected pace.

Enter minutes and seconds, for example 5:30.

Without a course, your plan uses time and pace to schedule fuel and hydration.

Fuel

Fuel

Pick the product you have trained with. MAVR will calculate the timing.

Using 92 g/h

Personalize the target

Personalize the target

Used only to adjust your recommendation.

Conditions and hydration

Conditions and hydration

Adjust for race-day weather and how you normally sweat.

Est. finish 3h 52m·42.2 km·25g/gel · with water
Calculator feedback
Want training-aware nutrition around this race?See MAVR on the App Store

How to use this calculator

Start with the race distance, then personalize the plan around the fuel you actually use in training.

1

Choose marathon as the race type, or connect a supported marathon course.

2

Enter target pace, gel carbs, body metrics, heat, sweat rate, and sweat saltiness.

3

Generate the plan to see gel timing, total carbs, hydration, sodium, caffeine, and pre-race carb targets.

The calculator builds a time-based plan when no course is selected.
Course-connected plans align fuel and water to mapped aid stations when course data is available.
You can override carbs per hour if your gut training or coach gives you a specific target.

Fuel calculator FAQ

Quick answers for race-day carbs, gel timing, hydration, and distance-specific fueling decisions.

How many gels do I need for a marathon?

Most marathon runners need about 5 to 10 gels, depending on finish time, grams of carbs per gel, and target carbs per hour. The calculator uses your target pace and product choice to calculate the exact count.

What should my marathon carbs per hour target be?

Many marathon plans land around 60 to 90 grams of carbs per hour. Faster, well-trained, or larger runners may target the higher end, while runners with GI sensitivity may start lower and train up.

When should I take my first marathon gel?

A practical marathon starting point is 20 to 30 minutes after the start. Taking fuel early helps maintain glycogen availability instead of waiting until fatigue is already building.

Related race fuel calculators

Half marathon fuel calculatorPlan a shorter 21.1 km race.Ultra marathon fuel calculatorPlan 50K, 50 mile, 100K, 100 mile, or custom ultras.Race course libraryBrowse mapped aid-station courses.