Endurance calculators.
Science-backed tools for runners, cyclists and triathletes. Used by Boston qualifiers and Kona finishers — no email wall, no upsell, no fluff.
Most popular
AI Nutrition Plan
Instant AI-generated race-day fueling plan: carbs/hour, sodium, fluids, product picks.
Open calculatorVDOT Race Predictor
Daniels VDOT from any race result. Predicts times across distances and gives E/M/T/I/R paces.
Open calculatorFTP & Power Zones
Estimate FTP from a 20-min or ramp test. Get 7 Coggan training zones and W/kg category.
Open calculatorHeart Rate Zones
5-zone HR breakdown using max HR or the Karvonen method with resting HR.
Open calculatorSweat & Sodium Loss
Calculate sweat rate and sodium loss from a simple weigh-in test. Build a real hydration plan.
Open calculatorCritical Swim Speed
Derive CSS from a 400m + 200m time trial. Get swim training zones in pool intervals.
Open calculatorMore training tools
Heat & Humidity Pace
Adjust running pace for temperature and humidity using dew point.
Open calculatorTriathlon Race Predictor
Predict Sprint, Olympic, 70.3 and Ironman splits from swim/bike/run pacing.
Open calculatorMarathon Pace & BQ Check
Convert goal time to per-km/mile pace and check it against your Boston Qualifying standard.
Open calculatorWeight & Pace Impact
See how a change in body weight affects running pace and cycling W/kg.
Open calculatorCarb Loading Plan
Personalized 3-day carb load by event distance. Grams per day + food equivalents.
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