How it works
The calculator starts with a baseline of about 35 ml per kilogram of body weight per day. That covers ordinary fluid losses from breathing, urine, and skin for a sedentary adult in a mild climate.
It then adds:
- Exercise: about 500–750 ml per hour of activity, depending on intensity and sweat rate.
- Hot or humid climate: a small additional bump for extra sweating and evaporative losses.
The result is a range, because thirst, sweat rate, and diet vary. Much of your fluid also comes from food — fruits, vegetables, soups, and yogurt all count toward hydration.
Limitations
Fluid needs are highly individual. Endurance athletes, people with kidney or heart conditions, those on diuretics, and pregnant or breastfeeding individuals may need personalized guidance. This calculator estimates total beverage and food-derived fluid; it does not prescribe a medical target.