Water intake calculator

How much water do you need?

Health authorities give adequate intakes of total water, which includes the water in food as well as drinks. The European Food Safety Authority recommends 2.0 liters a day for women and 2.5 liters for men in a temperate climate, with 0.3 L more in pregnancy and 0.7 L more when breastfeeding. About a fifth of that usually comes from food, especially fruit, vegetables and soups.

Worked example

A woman who exercises 30 minutes a day: 2.0 L × 80% from drinks = 1.6 L, plus about 0.375 L for the exercise = about 2 liters to drink, roughly 8 glasses of 250 mL (8 oz).

Signs you are drinking enough

• Pale yellow urine through the day.
• Rarely feeling thirsty.

You need more in hot weather, at altitude, with fever or vomiting, and during long or intense exercise. Coffee and tea count toward your intake. Drinking far more than you need is rarely helpful and, in extreme cases during endurance events, can be dangerous. The US National Academies give higher figures (about 2.7 L for women and 3.7 L for men of total water), mainly because they reflect observed US intakes.

The page starts from the EFSA adequate intake for your sex, adds the extra for pregnancy or breastfeeding, and assumes 80% comes from drinks and 20% from food. Exercise adds 0.75 liters per hour. Glasses are counted at 250 mL. Everything is calculated in your browser.