Smart Fueling Calculator

Calculate your fluid, carbohydrate, and sodium needs based on ACSM & Jeukendrup (2011) guidelines. Don't let bonking ruin your race day.

Body Weight (kg)

Run Duration

hrs

min

Run Intensity

Easy Z1–Z2

Tempo Z3–Z4

Hard Z4–Z5

Weather Conditions

Cool < 18°C

Moderate 18–28°C

Hot > 28°C

Why no carbs under 45 minutes?

Glycogen stores in your muscles and liver are sufficient for runs under ~75 minutes at moderate intensity. Consuming exogenous carbs this early primarily benefits very high-intensity sessions (>75% VO₂max) where a mouth rinse or small 20–30g intake can help performance via neural signaling.

Why up to 90g/hr for very long runs?

The intestine has separate transporters for glucose and fructose (SGLT1 and GLUT5). Using them simultaneously — roughly in a 2:1 ratio (e.g., maltodextrin + fructose) — allows absorption up to 90g/hr without GI distress. Single-source carbs max out at ~60g/hr due to transporter saturation. This is the Jeukendrup (2011) multiple-transportable-carbohydrate model.

How do I train my gut for high carb intake?

Start with 30–40g/hr and increase by 10g/hr every 2–3 weeks of long runs. Practice fueling during training runs, never try a new strategy on race day. GI distress from carbs is often a trainability issue, not just individual tolerance.

Crenoe App

Track how your body actually responds to your fueling

Connect Strava and Crenoe shows your Aerobic Decoupling, ACWR load management, and HR drift per run — so you can see whether your fueling is actually working over time.

Aerobic Decoupling HR Drift Analysis ACWR Load Mgmt Free to start

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