The ACSM exercise hydration protocol.
BEFORE
2 hours before
400–600ml
Pre-hydrate to start exercise well-hydrated
DURING
Every 15–20 min
150–350ml
Match sweat rate to prevent >2% body weight loss
AFTER
Within 2 hours
1.5× fluid lost
~750ml per lb of body weight lost through sweat
TIP: Drag the "Exercise Duration" slider to your daily workout time for an exercise-adjusted result
Your exercise-adjusted hydration intake.
STEP 01
Your profile.
Gender
Activity Level
Climate / Temperature
Enter your details
Your personalized hydration result will appear here.
Exercise hydration FAQ.
Follow the ACSM protocol: drink 400–600ml (14–22 oz) 2 hours before exercise, 150–350ml (5–12 oz) every 15–20 minutes during exercise, and 1.5× the fluid lost after exercise (roughly 750ml per pound of body weight lost). Our water intake calculator during exercise adds 500ml per 30 minutes of daily workout time to your baseline recommendation.
For exercise under 60 minutes at moderate intensity, plain water is sufficient. For longer sessions, high-intensity workouts, or exercise in heat, sports drinks with electrolytes (sodium, potassium, magnesium) help replace sweat losses and prevent hyponatremia. The rule of thumb: water for workouts under 60 minutes, electrolytes for anything longer or in hot conditions.
During a marathon, aim for 500–750ml per hour. Avoid drinking only plain water for runs over 90 minutes — add sodium via electrolytes to prevent hyponatremia. Weigh yourself before and after your long run; aim to lose no more than 2–3% of body weight. Pre-race: drink 500ml 2 hours before the start, then 150–250ml at the start line.