Find out how much water you should drink per day based on your body weight, activity level, and climate.
The baseline used here is about 33 ml per kilogram of body weight (roughly half an ounce per pound). On top of that, exercise adds around 350 ml (12 oz) per 30 minutes of activity, and warm or hot climates raise the total another 10-20%.
For a 75 kg (165 lb) person with 30 minutes of daily exercise in a temperate climate, that works out to about 2.8 liters (95 oz) per day.
All fluids count — water, tea, coffee, milk, and juice — and about 20% of daily fluid typically comes from food, especially fruit and vegetables. Caffeinated drinks are mildly diuretic but still contribute a clear net positive. Alcohol is the exception: it dehydrates more than it hydrates.
Needs go up when you're ill, pregnant or breastfeeding, at altitude, or training hard. If you're dialing in overall health numbers, our calorie calculator and BMI calculator complete the picture.
A common baseline is about 30-35 ml per kilogram of body weight (roughly half an ounce per pound), plus extra for exercise — around 12 oz (350 ml) for every 30 minutes of activity — and more in hot climates.
No. The "8x8" rule (eight 8-oz glasses, about 1.9 liters) is a rough average. Needs scale with body weight, activity, and climate — a 90 kg athlete in summer needs far more than 2 liters.
Yes. Despite mild diuretic effects, caffeinated drinks still provide a net positive fluid contribution. About 20% of daily fluid also comes from food.
Yes, though it's rare. Drinking many liters in a short period can dilute blood sodium (hyponatremia), which is dangerous. Spread intake through the day and let thirst guide you during long exercise.