Daily Water Intake Calculator
Find out how much water you should drink daily based on your weight, activity level, and climate.
How Much Water Do You Really Need?
Water intake needs are highly individual. The National Academies recommend roughly 91 oz (2.7 L) per day for women and 125 oz (3.7 L) for men from all beverages and food combined — but these figures assume average activity in a temperate climate. Anyone who exercises regularly, works outdoors, or lives in a hot environment needs significantly more.
The most reliable formula scales intake to body weight: approximately 0.5 oz per pound of body weight as a baseline. Layer on activity — every hour of exercise adds roughly 16–24 oz of sweat loss — and climate adjustments for heat and humidity. This produces a personalized target far more accurate than the generic "8 glasses" rule.
Timing matters as much as total volume. Spreading intake throughout the day keeps plasma osmolality stable, supports kidney function, and maintains cognitive performance. Large boluses consumed at once are mostly excreted. Aim for consistent, moderate sips from waking through the evening, and drink extra before, during, and after exercise.