How to use the water intake calculator
Choose your sex, whether you're pregnant or breastfeeding, and which official guideline to use. Add any exercise. You get a daily total, how much of it to drink and an extra allowance for exercise.
Official daily water guidelines
| Europe (EFSA) | US and Canada (National Academies) | |
|---|---|---|
| Men | 2.5 L | 3.7 L |
| Women | 2.0 L | 2.7 L |
| Pregnant | 2.3 L | 3.0 L |
| Breastfeeding | 2.6–2.7 L | 3.8 L |
These are total water from all drinks and food. For the European figures, about 20% usually comes from food, so about 80% is what to drink. The National Academies give their own figures for drinks: 3.0 L for men, 2.2 L for women, 2.3 L in pregnancy and 3.1 L while breastfeeding. The two figures differ because the bodies set them in different ways, not because Americans need more water.
Worked example
A woman using the European guideline needs about 2.0 L a day: about 1.6 L from drinks (6 glasses of 250 ml) and 0.4 L from food. With 45 minutes of exercise, add about 0.3 to 0.6 L.
What counts?
Water, milk, tea, coffee and other drinks all count, as does the water in food such as fruit, vegetables and soups. Thirst is a reliable guide for most healthy people; pale-yellow urine usually means you're drinking enough.
Planning meals as well? Try the calorie calculator.
Frequently asked questions
Is "8 glasses a day" right?
8 glasses of 250 ml is 2 L, the European total for women. But that total includes the water in food, so about 6 glasses from drinks is enough for many women. Men, active people and anyone in hot weather need more.
Can you drink too much water?
Yes. Drinking very large amounts quickly can dangerously lower blood sodium. Spread drinks through the day and don't force fluids beyond thirst unless a doctor advises it.
Sources
- EFSA (2010): Dietary reference values for water
- National Academies (2005): Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and Sulfate
- American College of Sports Medicine (2007): Exercise and fluid replacement
Formulas checked 29 October 2026. How we test our calculators. This calculator gives general estimates for adults and is not medical advice. Talk to a doctor or dietitian about your own health.