Exercise Hydration Calculator
Calculate how much water to drink before, during, and after exercise based on your body weight, sweat rate, and workout intensity.
Why Hydration Matters During Exercise Even mild dehydration (1-2% of body weight) impairs physical and cognitive performance. At 2% dehydration: aerobic capacity drops by 10-20%. At 4% dehydration: muscular endurance and strength decline significantly. At 6%+: serious heat illness risk.
Sweat Rate Varies by Individual Average sweat rate ranges from 0.8 to 2.4 liters per hour depending on:
- Body size (larger athletes sweat more)
- Exercise intensity
- Air temperature and humidity
- Acclimatization to heat
- Fitness level
Hydration Guidelines (NATA Position Statement) Pre-exercise: 17-20 oz of water 2 hours before; 7-10 oz 10-20 minutes before During exercise: 7-10 oz every 10-20 minutes Post-exercise: 24 oz for every pound of body weight lost
When Electrolytes Are Needed For exercise lasting over 60 minutes, water alone is insufficient. Sodium, potassium, and magnesium are lost in sweat. Sports drinks, electrolyte tablets, or salty snacks help replace these. Low sodium (hyponatremia) from drinking only water during long events is a real risk.
Simple Rule Drink to thirst for most workouts. Weigh yourself before and after to calibrate — every pound lost is roughly 16 oz of fluid to replace.
Signs of Dehydration
- Dark yellow or amber urine
- Dry mouth and lips
- Headache or lightheadedness
- Muscle cramps
- Reduced sweat rate late in session