How This Calculator Works
This planner uses evidence-based sports nutrition science to calculate your personal fueling targets. Calculate your targets in “Your Details” first — then use the other three tabs at the top of this tool to build your Ride Schedule, review Nutrition Guidelines with your personal targets in context, and verify your Pack Checklist before race day.
Here’s what drives each number:
Carbohydrates are the same for all rider sizes. Your gut — not your muscles — is the limiting factor. Research shows the small intestine can absorb roughly 60g of glucose per hour regardless of body size. For rides over 2.5 hours, combining glucose and fructose (which use different intestinal transporters) raises that ceiling to 90g/hr.
Fluid scales with your weight. Larger athletes have a greater total body surface area and higher absolute sweat rates. A 100lb rider and a 200lb rider at the same temperature and intensity will have meaningfully different fluid needs.
Sodium responds to temperature and intensity. Sweat sodium concentration is relatively consistent across body sizes, so it’s the rate of sweating that matters — and that’s driven by how hard you’re working and how hot it is. Higher intensity increases sweat rate; higher temperature does the same. Sodium targets range from 325mg/hr on an easy cool-weather ride up to 1,050mg/hr in very hot, hard conditions.
Duration multiplies everything. All totals scale directly with ride length — a 3-hour ride and a 6-hour ride will look very different even at identical weight, intensity and temperature.
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