Daily Water Intake Recommendations
Hydration needs vary based on body weight, physical activity, climate, and health status. General guidelines from the National Academies recommend about 3.7 liters (125 oz) per day for men and 2.7 liters (91 oz) for women, including water from food. The popular "8 glasses a day" rule is an approximation; actual needs are more individualized.
This calculator personalizes the estimate using your weight and activity level. Athletes and people in hot climates need significantly more — up to 1–1.5 liters per hour of intense exercise. Distributed throughout the day (not consumed all at once), water supports metabolism, kidney function, joint lubrication, and cognitive performance.