Free ultra running nutrition tool

Ultra marathon fuel calculator

Plan fuel for 50K, 50 mile, 100K, 100 mile, or custom ultra distances. The calculator uses MAVR's ultra race categories to estimate carb cadence, hydration, sodium, caffeine, and course-aware aid-station timing.

Use the calculatorDownload on the App Store

Distances

50K-100 mi

Includes fixed and custom ultra categories.

Carb target

60-120 g/h

Higher targets require gut training and product variety.

Logistics

Aid + carry

Use course data when available, then verify drop bags and refills.

Build your race fuel plan

Calculate an ultra marathon fueling plan from a 50K, 50 mile, 100K, 100 mile, or custom ultra distance, then adjust pace, gel product, carb target, body metrics, weather, and sweat profile.

Race setup
How it works: Pick a race type for the correct distance, including ultra presets. Without a course, MAVR builds a time-based plan from your pace, gel, carb target, body metrics, weather, and sweat profile. With a course connected, the plan lines up fuel and water with known aid stations.
Gel selection

Recommended: 92g/h based on your profile

Personal metrics
Race conditions
Est. finish 4h 35m·50 km·25g/gel · with water

How to use this calculator

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

1

Choose 50K, 50 mile, 100K, 100 mile, or custom ultra as the race type.

2

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

3

Generate the plan to review fuel cadence, total carbs, fluid, sodium, caffeine, and pre-race carb targets.

Ultra plans should be rehearsed in long runs because GI tolerance, terrain, and pace variability matter more over long durations.
For course-connected ultras, verify drop bags, crew access, refill points, and aid-station inventory before race day.
Use the carb override if your trained gut can handle a higher target or if your coach has prescribed a specific intake.

Fuel calculator FAQ

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

How much fuel do I need for an ultra marathon?

Many ultra runners target 60 to 90 grams of carbs per hour, while highly trained guts may work toward 100 to 120 grams per hour for very long events. The calculator estimates the total from your expected duration and chosen carb target.

Can I use this for 50K, 50 mile, 100K, and 100 mile races?

Yes. The website calculator now includes fixed ultra presets for 50K, 50 mile, 100K, and 100 mile races, plus a custom ultra distance option for events 45 km and longer.

Should an ultra plan include more than gels?

Usually yes. Gels can anchor carb cadence, but long ultras often need drink mix, chews, sodium, water refill planning, and sometimes savory foods or protein depending on duration and gut tolerance.

Related race fuel calculators

Marathon fuel calculatorPlan a full road marathon.Half marathon fuel calculatorPlan a 21.1 km race.Race course libraryBrowse mapped race aid stations.