How much water do you really need?
The U.S. National Academies set adequate total water intakes of about 3.7 liters a day for men and 2.7 liters for women, including water from food. A common practical rule is about 30–35 ml per kg of body weight from drinks, plus extra for sweat.
Adjusting for exercise and heat
Add roughly 350–500 ml (12–17 oz) for every 30 minutes of exercise, and more in hot or humid weather. For long, sweaty sessions over an hour, include electrolytes, not just water.
Simple checks
Pale yellow urine and rarely feeling thirsty are good signs you're drinking enough. Very clear urine all day can mean you're overdoing it. More isn't always better.
Frequently asked questions
Do coffee and tea count toward water intake?
Yes. Moderate amounts of caffeinated drinks still hydrate you overall.
Is 8 glasses a day right?
It's a reasonable starting point (about 2 liters) for many people, but needs vary with size, activity and climate.
Can you drink too much water?
Yes. Drinking several liters in a short time can dangerously dilute blood sodium (hyponatremia). Spread intake across the day and use electrolytes during long endurance events.
These results are estimates for healthy adults and are not medical advice. If you are pregnant, breastfeeding, under 18, or managing a medical condition, talk to your doctor or a registered dietitian.