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
Grade Adjusted Pace (GAP)
Convert hilly running pace to flat-equivalent GAP using the Minetti energy-cost model — same as Strava.
Open calculatorVDOT Pace Chart
Full Jack Daniels pace table — E/M/T/I/R paces and 5K/10K/half/marathon times for VDOT 30 to 85.
Open calculatorDew Point for Runners
Magnus-Tetens dew point from temperature + humidity, mapped to a runner-specific comfort scale.
Open calculatorHeat & Humidity Pace
Adjust running pace for temperature and humidity using heat index.
Open calculatorTriathlon Race Predictor
Physics-based bike model with race elevation. Predicts Sprint, Olympic, 70.3 and IM.
Open calculatorHalf Ironman 70.3 Predictor
Predict your 70.3 finish time and splits from training paces. Metric or imperial (US) units. Transitions baked in.
Open calculatorAI Bike Fit Analyzer
Real-time MediaPipe pose detection from your webcam. Measures knee, hip, back, ankle, arm & torso angles.
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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