How Much Water Should You Drink a Day?

About 2.2–3.0 liters (L) of beverages a day is a general starting point for adults, not a requirement for plain water. The water intake calculator can help you explore a starting point. Age, pregnancy, breastfeeding, activity, heat, altitude, illness and medical conditions can change your needs.

Good hydration comes from both food and drinks. The figures below are adequate intakes for groups of generally healthy people, not exact amounts every person must reach each day.

How much water do adults need each day?

The National Academies recommend the following daily total water intakes. Total water includes water in food as well as all beverages, including plain water.

For adults, food supplies roughly 20% of total water on average. That is why the approximate beverage amounts for women and men are lower than the total-water figures. The actual amount from food varies with what you eat, so these beverage figures are starting points rather than precise targets.

You do not need to drink the full total-water amount as plain water on top of other drinks and food. Water is a convenient choice, but other beverages also contribute. Spread drinks throughout the day rather than trying to consume a large amount at once.

What changes how much water you need?

Activity and heat

Physical activity and hot weather can increase fluid needs because you lose water through sweat. The amount varies with the activity, conditions and person, so a single daily target cannot account for every situation.

Pay attention to thirst and make fluids available during and after activity. If you are exercising in heat or for a long time, your needs may be different from those on a quiet day indoors.

Age, pregnancy and breastfeeding

Children need different amounts from adults. The National Academies' daily adequate intakes for total water from food and beverages are:

These are not plain-water prescriptions for children. Ask a child's healthcare professional for individual advice, especially during illness or if you are concerned about their fluid intake.

Pregnancy and breastfeeding also change total-water needs, as shown in the adult table. A healthcare professional can help adapt those figures to an individual's circumstances.

Illness, altitude and health conditions

Fluid needs may rise at altitude or during an illness that causes vomiting, diarrhea or fever. If you cannot keep fluids down or are concerned about dehydration, contact a healthcare professional rather than relying on a daily target.

Some people need to limit fluids rather than increase them. Kidney disease, heart failure and certain medications, including diuretics, can affect fluid advice. Follow your clinician's instructions if you have a prescribed fluid limit, and ask before changing it.

Seek urgent medical care for confusion, fainting or other severe symptoms, particularly if dehydration or excessive water intake is a concern. Drinking excessive water quickly can also be dangerous; more is not always better.

How can you use a water intake calculator?

Use the calculator linked above as a starting point, then compare its estimate with the guidance for your age and circumstances. A calculator cannot account for every medical condition, medication or change in your daily routine.

Think of the result as a guide to discuss or adjust, not a quota to force yourself to meet. If you have a medical fluid restriction, that advice takes priority over a calculator estimate.

Drinking enough supports normal body function, including the organs involved in waste removal. Your liver and kidneys do most of the body's detoxification, while the lungs and gut also help eliminate waste; drinking extra water does not flush toxins from the body.