Estimate hydration and calorie needs for your trail run to avoid bonking. No GPX needed — just enter your route numbers.
Estimated duration: 15h 0m
Hydration is estimated at ~500 ml/hour base rate, adjusted +15% per 5°C above 20°C. Calorie burn uses ~8 kcal/kg/hour as a rough trail running baseline. These are estimates — adjust based on your experience.
Bonking — running out of glycogen — is the most common reason trail runners slow down or DNF in ultras. Your body can only store about 2,000 kcal of glycogen, but a 50K mountain run can burn 4,000–6,000 kcal. The gap has to be covered by eating and drinking during the effort.
Dehydration compounds the problem: even a 2% fluid loss reduces endurance performance measurably. In hot conditions or at altitude, sweat rates climb and the margin shrinks. Planning your nutrition and hydration before race day — and knowing how many gels, bars, or liters you need per aid-station interval — prevents the guesswork that leads to stomach trouble or energy crashes.
All calculations happen in your browser. Nothing is sent to a server.