Carbohydrate Fuelling Calculator
What Is Carbohydrate (CHO) Fueling?
Carbohydrate is the primary fuel for moderate‑to‑high intensity endurance exercise, supplying up to 80 % of energy at threshold intensities. Ingesting exogenous CHO during prolonged efforts maintains blood glucose, spares muscle glycogen and delays fatigue .
Why Use a Mass‑Relative Anchor?
Absolute targets (e.g. 60 g/h) may under‑fuel larger athletes and over‑fuel smaller ones. Anchoring intake to 0.4–0.7 g/kg/h scales recommendations to body mass—so a 50 kg athlete needs ~20–35 g/h, while an 80 kg athlete needs ~32–56 g/h .
Standard vs High‑Carb Strategies
Standard (0.4–0.7 g/kg/h): Suits most sessions up to 2 h, capping at ~90 g/h for longer workouts.
High‑Carb (0.8–1.2 g/kg/h, up to 120 g/h): Requires mixed glucose + fructose blends (“multiple‑transportable” CHO) to achieve higher oxidation rates (up to ~1.2 g/min) with minimal GI distress .
Adjusting for Temperature
Heat increases metabolic rate and CHO oxidation by ~10 % for every 5 °C above 20 °C. We apply a +2 % CHO adjustment per °C > 20 °C to ensure fuel supply meets elevated demands .
Adjusting for Altitude
At moderate–high elevations (1 500–3 000 m), carbohydrate cost rises ~10 % per 1 000 m due to increased ventilatory and metabolic work. We apply a +10 % CHO adjustment per 1 000 m to compensate for these added demands .
Why Log GI Symptoms?
Up to 70 % of endurance athletes experience exercise‑induced GI issues (nausea, cramps, bloating). Recording symptom type, severity (0–4) and timing (pre/mid/post) helps correlate specific CHO formats and rates with tolerance, guiding personalised gut‑training strategies .
How to Use the Calculator
Enter your body mass, session duration and chosen fueling strategy (Standard or High‑Carb).
Specify planned CHO intake (g/h) and CHO format (drink, gel, bar, mixed).
Provide ambient temperature and altitude to generate both sea‑level and environment‑adjusted CHO targets.
Log any GI symptoms to refine future intake strategies.
By following mass‑relative, environmental and GI‑tolerance principles, this tool helps you personalise CHO fueling for optimal performance and comfort.