Race Nutrition Planner

Bonking late in a race usually traces back to a fueling plan that was a guess. Carbs, fluid, and sodium each have a defendable hourly range, and your finishing time decides how much of each you need to carry. The calculator above takes your race duration and your hourly rates and gives you the totals to pack plus the per-hour numbers to hit.

What the plan covers

The planner works from race duration in hours and three hourly inputs. Each one has a range backed by what the gut and sweat can handle, not a single magic figure.

• Carbs per hour: pick 60, 75, 90, or 120 g/hr. 60-90 g/hr suits most athletes. 120 g/hr is only realistic with a glucose-fructose mix and a gut you have trained to absorb it.
• Fluid per hour: 0.4-0.8 L/hr depending on heat, body size, and thirst. Hot day, big athlete, more fluid.
• Sweat sodium: 300-1000 mg/L. A salty sweater leaves white crust on a black kit and needs the high end.

From those it returns total carbs, carbs per hour, total fluid in litres, total sodium in mg, and sodium per hour.

Reading the numbers

The per-hour figures are what you rehearse. The totals are what you load into bottles, flasks, and pockets before the start.

Say you plan a five-hour race at 90 g/hr carbs, 0.6 L/hr fluid, and 800 mg/L sweat sodium. That is 450 g of carbohydrate, 3 litres of fluid, and the sodium total to match. Work backwards into product: a gel is roughly 25 g carbs, a 500 ml mix bottle might carry 40 g. Now you know how many of each to start with and how many to grab at aid stations.

Sodium tracks fluid. Higher sweat rate and saltier sweat both push the milligrams up. If you cramp late or finish bloated and headachey, your sodium-to-fluid balance is the first place to look.

Practice it, never trial it on race day

The biggest mistake is testing a fueling plan for the first time on race morning. A gut that absorbs 90 g/hr is trained, not given. Run your race-day carbs, fluids, and products in your long sessions for weeks first, at race intensity where blood flow leaves the stomach. Find out which flavours turn on you at hour four when you are tired and breathing hard. The plan that works in training is the only one you trust on the start line.

For how to build fueling into your weekly long sessions, read the fueling around long sessions guide.