Daily water intake calculator
Estimate how much water to drink a day from your weight, activity and climate. It runs in your browser: nothing you enter is stored or sent anywhere.
How this estimate works
It starts at 33 ml of water per kilogram of body weight, scales that for activity (up to 1.4 times), adds 200 to 800 ml for warmer weather, and adds 300 ml for pregnancy or 700 ml for breastfeeding. Results are kept between 1.5 and 5 litres. The 33 ml per kilogram factor is a common rule of thumb, not a figure from a clinical guideline.
The result is an estimate of total water per day, which includes the roughly 20 to 30 percent that usually comes from food. If you eat plenty of fruit, vegetables and soup, you may need to drink somewhat less than the total.
Reference intakes from health bodies
These are adequate intakes for total water for adults, not requirements, and they are not set by this page.
- EFSA (2010), Scientific Opinion on Dietary Reference Values for water: 2.0 L for women and 2.5 L for men, plus about 0.3 L in pregnancy and 0.7 L while breastfeeding.
- US National Academies, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005; also used by Health Canada): 2.7 L for women and 3.7 L for men of total water, of which about 2.2 L and 3.0 L come from drinks.
- NHMRC, Nutrient Reference Values for Australia and New Zealand (2006): 2.8 L for women and 3.4 L for men.
The World Health Organization does not publish a single daily drinking target for adults. This page is not affiliated with or endorsed by EFSA, the National Academies, NHMRC, Health Canada or the WHO.
Common questions
How much water should I drink a day?
There is no single number. Published adequate intakes for total water, which includes water from food and other drinks, are about 2.0 L for women and 2.5 L for men (EFSA 2010), 2.7 L and 3.7 L (US National Academies 2005), and 2.8 L and 3.4 L (NHMRC Australia and New Zealand 2006). Needs rise with body size, heat and exercise.
Does food count toward daily water intake?
Yes. Reference intakes cover total water, and food usually supplies roughly 20 to 30 percent of it, so the amount you need to drink is lower than the total.
How much more water do pregnant or breastfeeding women need?
EFSA suggests about 300 ml more per day in pregnancy and about 700 ml more while breastfeeding. Ask your doctor or midwife for advice that fits you.
Can you drink too much water?
Yes. Drinking far more than your body can excrete, roughly above 0.7 to 1.0 litres per hour, can dilute blood sodium (hyponatremia). Spread your intake across the day and drink to thirst while exercising.
Why does the calculator show no number for kidney or heart conditions?
People with these conditions are often given a fluid target or limit by their doctor, and a general estimate could be wrong for them.
WaterSip tracks your intake with reminders, home-screen widgets and on-device privacy.
This calculator provides general information only. It is not a medical device and not medical advice. Your needs depend on your health, medication, diet and activity. Please ask your doctor before changing how much you drink, especially if you are pregnant, have a medical condition, or take medication that affects fluids.