Race-day fueling calculator

What it does

The race-day fueling calculator builds a complete nutrition plan for a triathlon — carbs per hour, fluid per hour, sodium per hour, caffeine schedule — broken down per leg (swim / bike / run) plus transition (T0 / T1 / T2) nutrition. Outputs include warnings when the plan runs short on any axis and a carried- products inventory so you can pack the right number of gels, chews, drink mixes, and salt tabs.

URL: /calculators/ then open Fueling. Or open the triathlon-specific variant directly at /static/calculators/triathlon_fueling_calculator.html.

Inputs the form asks for

Athlete

• Height (cm or in).
• Weight (kg or lb).

Conditions

• Conditions (select) — temperature / humidity band.
• Bike Sweat Rate (L/h) — your measured sweat rate on the bike at race intensity.
• Run Sweat Rate (L/h) — your measured sweat rate running at race intensity.
• Sweat Type (select).
• Sweat Sodium (mg/L) — your measured sweat sodium concentration.

Run the sweat rate calculator beforehand if you don't know the numbers.

Race

• Race Distance (select: sprint / Olympic / 70.3 / Ironman).
• Race Start (time of day).
• Swim time (min).
• Bike time (min).
• Run time (min).

Pacing

• Bike Power (W) — average power you plan to hold on the bike leg. Drives the bike CHO requirement.

Fueling strategy

• Fueling Mode — Minimum / Recommended / Maximum (sets the CHO/h target band).
• Run CHO vs Bike factor — multiplier on run CHO (typically 0.6-0.9 because absorption drops while running).
• Caffeine Strategy — None / Conservative / Standard / Aggressive (drives caffeine timing across the race).
• Starting Glycogen — Fasted / Normal / Carb-loaded.
• Bike CHO Override (g/h, optional) — replaces the calculated bike CHO target with a fixed value.
• Run CHO Override (g/h, optional) — same for run.
• Bike Fluid Replacement % — fraction of bike sweat loss you intend to replace.
• Run Fluid Replacement % — same for run.
• Auto-use tabs — whether to add electrolyte tabs to make up sodium when carried drinks fall short.

Carried products

For BOTH bike and run independently:

• 3 drink mix slots — pick product + bottle count.
• 3 gel slots — pick product + count.
• 2 electrolyte / salt tab slots — pick product + count.

Transitions

For each of T0 (pre-race) / T1 (swim→bike) / T2 (bike→run):

• Enable transition nutrition (checkbox).
• Product for each slot in that transition.
• Count of each product taken.
• Time relative to race start (or relative to transition).

Aid stations

• Enable bike aid-station toggle (checkbox).
• Enable run aid-station toggle (checkbox).

When enabled, aid-station fluid / CHO availability is folded into the carry plan so you don't have to bring the entire race on your person.

Outputs

• Per-leg CHO/h, fluid/h, sodium/h targets with the totals for the full race.
• Carry plan — exactly which products to put in your bike bottles, gel pockets, and run belt to hit the target.
• Transition nutrition — what to consume at T0/T1/T2 and when.
• Warnings:
• CHO/h falls short of mode target on bike or run.
• Fluid replacement below the configured threshold.
• Sodium replacement insufficient for sweat type.
• Caffeine schedule too aggressive given starting glycogen.
• Carried products don't supply enough for the bike or run leg.

How to use it

1. Run a sweat rate test at the conditions you expect on race day. Plug bike + run sweat rates and sodium into this calculator.
2. Pick your fueling mode based on tolerance (Minimum for sensitive stomachs, Maximum for elite gut training).
3. Set the carried products to what you actually plan to carry. Adjust counts up if a warning appears.
4. If using aid stations, toggle them on and tune the carry plan down accordingly.

See also: Sweat rate calculator, Sweat Rate Test assessment, Race readiness checklist.