Daily Water Intake Calculator

About this calculator

A commonly cited hydration guideline suggests drinking roughly 33 millilitres of water per kilogram of body weight per day (equivalent to about 0.5 fl oz per pound), which scales fluid needs directly to body size rather than prescribing a flat "eight glasses a day" target that ignores how much a person actually weighs. This is a baseline estimate for a sedentary adult in a temperate climate — actual needs rise with exercise, heat, altitude, pregnancy/breastfeeding, and illness, and total fluid intake includes water from food and other beverages, not just plain drinking water.

Dietitians, athletic trainers and general health guidelines use weight-based hydration targets like this because thirst alone is an imperfect and delayed signal — by the time you feel thirsty, mild dehydration has often already set in — so having a concrete daily number gives people, especially athletes and older adults (whose thirst sensation weakens with age), a practical target to track against rather than relying on subjective feel.

This calculator takes your body weight and returns a suggested daily water intake target based on the 33 ml per kg guideline.