Race Nutrition Calculator

What the body needs on race day

In long events, fuelling co-determines the result. The calculator tells you how much carbohydrate, fluid and sodium per hour makes sense.

The values depend on duration and intensity: under an hour you need practically nothing; beyond three hours intake becomes the decisive factor.

How it is calculated

Carbohydrates per hour follow the duration: under 1 h none, up to 1.5 h 30 g, up to 2.5 h 60 g, up to 3 h 75 g, from 3 h 90 g. High intensity adds 10 g, capped at 90 g. Fluid: 500 ml/h, 700 ml/h in heat, plus 200 ml at high intensity. Sodium: 450 mg/h, 700 mg/h in heat.

The gut absorbs only about 60 g of glucose per hour; anything above that needs a second sugar (fructose), which is why the calculator recommends mixed sources at a 2:1 ratio from 2.5 h onwards.

Example: 3:30 h, moderate intensity, no heat. 90 g × 3.5 = 315 g of carbohydrate, 500 ml × 3.5 = 1.75 l of fluid, 450 mg × 3.5 = 1575 mg of sodium.

Body weight does not enter these formulas: gut absorption barely depends on it, but it does depend on practice — 90 g/h has to be trained.

To calculate race nutrition that actually works, test the plan in a long session before you trust it on race day.

The most important rule

Never try anything for the first time on race day. Your gut has to be used to the amounts, otherwise it rebels exactly when it matters.

And more is not better. Absorption is limited; take too much at once and it sits in your stomach instead of your muscles.

Frequently asked questions

How many carbohydrates per hour?

Between 30 and 90 grams depending on duration. The higher amounts only work with a mix of sugar types and need practice.

How much should I drink?

Enough that you lose no more than two to three percent of body weight. The sweat loss calculator finds your personal rate.

Do I need salt tablets?

In heat and long events often yes; otherwise most sports drinks suffice. Heavy, salty sweaters need more.