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Ultra · 50K to 100 mi

Ultra Fueling Calculator

Carb budgets, solid-food share, protein targets, sodium, and aid-station cadence for 50K, 50 mi, 100K, and 100 mi races.

Updated 17 April 2026 · Marcus Redd, Head Coach

Quick answer

Most ultra-runners need 150-300 kcal/hour split across gels, solid food, and salty options. Plan 40-90 g of carbs/hour (lower ceiling than marathon because the gut slows), 400-800 mL fluid/hour, and 500-1000 mg sodium/hour. Add 5-10 g protein/hour after hour four.

Your race

How this plan is built

Ultra fueling isn't a scaled-up marathon plan. Three things change:

1. The gut ceiling lowers over time

A trained marathoner's gut absorbs 90 g/h of 2:1 glucose-fructose for 3-4 hours. Past that, gastric emptying slows, sugar fatigue sets in, and forcing more carb causes GI distress. We scale target carb intake downward for longer races: 80-90 g/h for a 50K, 60-80 g/h for a 50-miler, 50-65 g/h for a 100-miler.

2. Calories come from multiple sources

Solid food, fat, and protein add calories without adding to the carb absorption load. For races over 6 hours we plan 40-60% of calories from non-gel sources after hour three. Typical solids: boiled salted potatoes, quesadillas, rice balls, peanut butter tortillas, broth.

3. Sodium scales with duration

Over 8 hours of sweating is where hyponatremia risk rises sharply. We target 500-1000 mg sodium/hour in ultras, higher in heat. Electrolyte capsules (200-300 mg/cap) are a backup to salty food, not the primary source.

Aid station strategy

Use every aid station after mile 15. Even if you feel great. Two simple rules:

  1. Top off and eat something. Never leave an aid station without at least one bite of real food and full bottles.
  2. One warm, one cold. Broth or quesadilla + watermelon or pickle. This keeps both hot and cold comfort options available as the day shifts.

Read next

For the full race-day playbook: Ultra Running Fueling Strategy.