Water intake calculator

How this calculator works

It starts from the adequate intakes set by the European Food Safety Authority (EFSA) for adults in a mild climate with moderate activity: about 2.0 litres of water a day for women and 2.5 litres for men. That figure is total water, from food as well as drinks. EFSA assumes about a fifth comes from food, so the calculator shows the rest as the amount to drink.

It then adds:

• 300 ml a day in pregnancy and 700 ml while breastfeeding, as EFSA recommends.
• About 0.5 to 1 litre for each hour of exercise. How much people sweat varies a lot, from about 0.3 litres to more than 2 litres an hour, depending on body size, effort and heat, so this is shown as a range.

Treat the result as a rough guide

• For most healthy adults, thirst is a reliable guide. Pale straw-coloured urine usually means you’re drinking enough.
• You need more in hot weather, and when you are ill with fever, vomiting or diarrhoea.
• Tea, coffee, milk and other drinks count. So does food with a lot of water, such as fruit, vegetables and soup.
• The US National Academies give higher figures (about 2.7 litres a day for women and 3.7 litres for men, including food), because they are based on what healthy people typically consume.
• If a doctor has told you to limit fluids, for example because of a heart or kidney condition, follow that advice instead.

Read the full article: How much water do you really need a day?

Sources and further reading

• EFSA Panel on Dietetic Products, Nutrition and Allergies (2010). Scientific opinion on dietary reference values for water. EFSA Journal, 8(3), 1459.
• National Academies (2004). Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate.
• American College of Sports Medicine (2007). Exercise and fluid replacement (position stand). Medicine & Science in Sports & Exercise, 39(2), 377–390.
• NHS: Water, drinks and your health