Quick estimate of how much energy you burn across each discipline. Pick the sport, plug in distance and intensity, get the calorie figure. Useful for fueling planning, not a substitute for a metabolic profile.
Each sport has its own input set. Switch between metric and imperial as needed, conversions happen behind the scenes, so the formulas always run on metric.
It’s an estimate. The order of magnitude is right; the last 20–30% takes lab data.
Run, bike (no power), and swim use simple body-mass × distance multiplied by an effort coefficient. Ignores wind, hills, drafting, fitness. Population-average estimates.
If you have a power meter, the Bike (power) tab is materially better, based on actual joules at the crank, divided by ~24% gross efficiency. Within ~10% of metabolic-cart truth for most cyclists.
Indirect calorimetry (mask + gas analysis) measures your oxygen uptake and respiratory exchange ratio, turns into a precise kcal/min for your physiology, not a population average.
Use this calculator to plan fueling (rough total to target on race day). Don’t use it to set weight-loss budgets, the error band is too wide for that.
Total calories burned is one number. What actually matters race-week is when you burn them, what fuel mix (fat vs. carb) at each intensity, and how much of that you can replace with what you can stomach, usually 60–90 g carbs/h for most athletes.
A typical Ironman athlete burns 7 000–10 000 kcal over the day, and replaces 30–40% of it with on-course fueling. The rest comes from glycogen and fat stores. Plan to replace what your gut can absorb, not what you burn.
Two ways to make this real:
Total calorie estimate → carb target → food equivalents.
Open → Sweat ratePair calorie burn with fluid + sodium loss for a complete fueling picture.
Open → All calculatorsBack to the full catalog, 30+ endurance calculators across performance, fueling, swim, bike, run.
Browse →Indirect calorimetry at the lab measures the gases you breathe, gives you a precise calorie burn rate by intensity, plus your fat/carb crossover. Worth its weight in gold for long-course fueling.
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