Triathlon Calorie Calculator

What it does

The Calorie Calculator estimates total energy expenditure for each leg of the race based on the athlete's weight, sport choice, and per-leg conditions. The total feeds the Fueling calculator at the following wizard step.

URL: /calculators/ then open the Calorie entry. Direct path: /static/calculators/triathlon_calorie_calculator.html. Wizard step 6.

Inputs the form asks for

Setup

Unit system: metric or imperial.
Sport selection: which legs to include (full triathlon, swim only, bike only, run only, duathlon, etc.).

Swim leg

Weight (kg).
Gender (affects RMR scaling).
Distance (km).
Time per 100 m (seconds): target swim pace.
Environmental conditions: pool, lake, ocean. Drives drag cost.
Difficulty: easy, moderate, hard, race effort.
Swim economy: elite / trained age-grouper / novice. Swimming energy cost varies more with technique than any other input — an elite swimmer covers the same kilometre on 30–40 % fewer calories than an adult-onset swimmer. The selector scales the estimate (elite ×1.0, trained ×1.35 — the default — novice ×1.7). The June 2026 logic audit found the unscaled formula read ~25–35 % low for typical age-groupers; pick the band that honestly matches the athlete's swim background.

Bike leg

Weight (kg).
Distance (km).
Plus environmental factors (wind, terrain).

Bike (power)

Power (watts) and Duration (minutes).
Gross efficiency (%): how much metabolic energy becomes mechanical work. Calories = mechanical work ÷ (4.184 × GE). Left at the default 23.9 % this matches the classic "kilojoules ≈ kilocalories" shortcut. If the athlete has done a metabolic test, enter their measured GE (the per-stage GE column on the test report — typically 18–24 % cycling); a lower efficiency correctly raises the calorie estimate for the same power.

Run leg

Weight (kg).
Distance (km).
Plus pace and environmental factors.

Outputs

Total calories across the full race (saved key output: calTotal).
Per-leg calorie totals.

Why calories matter

Calorie burn is the cap on what you need to replace with in-race fueling. The fueling calculator scales fueling against both calorie burn and CHO oxidation rate; a high-calorie leg needs proportional fuel.

When to rerun

When body weight changes by more than a couple of kg.
When race conditions change (hot day pushes burn up).
When you change projected pacing (faster pacing = more calories per hour).