Water is the molecule fundamental to our lives and to those of the majority of organisms on our planet. So much so that it is commonly said: "where there is water, there is life!" But how much water should you drink per day? What is the right amount, calculated on the basis of sex, age and weight?

How much water should you drink per day?

Our body is made up of 70 per cent water, with percentages that can range from 55 per cent to 75 per cent depending on the conditions mentioned above. It is the molecule that takes part in the majority of reactions inside our body — from the cell, through the muscles, brain and intestine. Water, for example, acts as a solvent for the main organic reactions and as a carrier, both of the nutrients essential to cell life and of the various compounds involved in organic processes that enable our survival. Here we explain how much water to drink per day.

The recommended amount of water to drink is approximately 30 ml per kilogram of body weight. An adult man weighing 80 kg should therefore take in around 2.5 litres of water per day — not forgetting the water also consumed through fruit and vegetables.

Water to drink, tap water is best

Tap water is sustainable and is a zero-kilometre product. Only a few minutes pass from the moment it is drawn from wells to when it comes out of our tap at home — it is fresh that very day. Tap water is low in sodium, has a hardness level (concentration of mineral salts) within legal limits, and aids diuresis. The important thing is to ensure an adequate intake of water throughout the entire course of the day. Tap water is also recommended for pregnant women and during breastfeeding, preferably with good levels of dissolved calcium salts — that is, with a calcium content above 200 mg/l.

Here is how much water to drink per day

Depending on age, the recommendations are:

• newborns up to six months of age: 100 ml per day

• between 6 months and one year of age: 800–1,000 ml/day
• between 1 and 3 years of age: 1,100–1,300 ml/day
• between 4 and 8 years of age: 1,600 ml/day
• between 9 and 13 years of age: 2,100 ml/day for boys and 1,900 ml/day for girls

• teenagers, adults and older adults:
  • females 2 L/day
  • males 2.5 L/day.

• For pregnant women, Efsa does not identify a daily requirement but suggests increasing the adult reference value by 300 ml/day. For breastfeeding women, the value rises to 700 ml/day.