How is it calculated?
Daily water intake is the estimated amount of fluid your body needs throughout the day to function properly. Water is needed for regulating temperature, transporting nutrients, protecting joints and removing waste.
There is no single exact formula; the most common approach is based on body weight. Roughly 30–35 ml per kilogram is recommended; Calxin uses 33 ml, the middle of that range:
Exercise level is also taken into account; since water is lost through sweat during activity, a certain amount is added as activity increases.
The exercise add-on accounts for average fluid loss; during long workouts, in hot weather or with heavy sweating the need can go beyond it. Water from food (especially vegetables and fruit) also covers part of the daily total. At very high body weights, a weight-based calculation can overstate the need.