The amount of drinking water required is variable.
 It depends on physical activity, age, health, and environmental conditions.
 In a temperate climate under normal conditions, adequate water intake is about 2.7 litres (95 imp fl oz; 91 US fl oz) for adult women and 3.7 litres (130 imp fl oz; 130 US fl oz) for adult men.
 Physical exercise and heat exposure cause loss of water and therefore may induce thirst and greater water intake.
 Physically active individuals in hot climates may have total daily water needs of 6 litres (210 imp fl oz; 200 US fl oz) or more.
European Food Safety Authority recommends 2.0 litres (70 imp fl oz; 68 US fl oz) per day for adult women and 2.5 litres (88 imp fl oz; 85 US fl oz) per day for adult men.
In the United States, the
reference daily intake (RDI) for total water is 3.7 litres per day (L/day) for human males older than 18, and 2.7 L/day for human females older than 18 which includes drinking water, water in beverages, and water contained in food.
 An individual's thirst provides a better guide for how much water they require rather than a specific, fixed quantity.
Water makes up about 60% of the body weight in men and 55% of weight in women.
 A baby is composed of about 70% to 80% water while the elderly are composed of around 45%.
The drinking water contribution to mineral nutrients intake is also unclear.
Inorganic minerals generally enter surface water and ground water via
runoff or through the Earth's crust. Treatment processes also lead to the presence of some minerals. Examples include
 Water generated from the
metabolism of nutrients provides a significant proportion of the daily water requirements for some
desert animals, but provides only a small fraction of a human's necessary intake. There are a variety of trace elements present in virtually all potable water, some of which play a role in metabolism. For example, sodium,
chloride are common chemicals found in small quantities in most waters, and these elements play a role in body metabolism. Other elements such as
fluoride, while beneficial in low concentrations, can cause dental problems and other issues when present at high levels.
Fluid balance is key. Profuse sweating can increase the need for
electrolyte (salt) replacement.
Water intoxication (which results in
hyponatremia), the process of consuming too much water too quickly, can be fatal.