How the estimate works
A common rule of thumb is about 35 mL per kg of body weight per day, plus extra for exercise (about 0.4–0.8 L per hour, more in heat) and hot or dry weather.
For reference, the European Food Safety Authority (EFSA) sets adequate total water intake at 2.0 L/day for women and 2.5 L/day for men. "Total" includes water from food, which usually provides about 20%.
Listen to your body
Thirst and pale-yellow urine are practical guides for most healthy adults. Needs rise with fever, vomiting, diarrhea, heat and long exercise.
Frequently asked questions
Do coffee and tea count?
Yes, they count toward fluid intake for regular drinkers.
Can I drink too much water?
Yes. Very large amounts in a short time — especially during endurance events — can cause dangerously low blood sodium. Drink to thirst.
I have kidney or heart disease. Does this apply?
No. Some conditions require limiting fluids; follow your doctor's instructions.