How much water should you drink a day?

2026-10-30

Most healthy adults do well with about 2 to 2.7 liters (68–91 fl oz) of total water a day for women and 2.5 to 3.7 liters (85–125 fl oz) for men. The lower figures come from the European Food Safety Authority (EFSA), the higher ones from the US National Academies. Both include the water in your food, so the amount you actually need to drink is lower: roughly 1.5–2.2 liters for women and 2–3 liters for men, more if you sweat a lot.

The two official numbers

There is no single global figure, but two expert bodies have done the most thorough reviews.

EFSA (Europe, 2010): an adequate intake of 2.0 liters a day for women and 2.5 liters for men. These values apply to "moderate environmental temperature and moderate physical activity levels", as the EFSA scientific opinion on water puts it.
US National Academies (2004): about 2.7 liters a day for women and 3.7 liters for men. Their report announcement adds that the vast majority of healthy people meet their needs "by letting thirst be their guide".

Neither is a strict minimum. Both are adequate intakes: amounts that healthy, well-hydrated people typically consume. Plenty of people stay perfectly well on less, and some need more.

Why the numbers differ

The US figures are based on what Americans in national surveys actually took in, and the European ones on European intake data. Different eating habits, climates and body sizes lead to different averages. Treat the gap as a reasonable range rather than a contradiction: somewhere between the two is a sensible target for most adults.

What "total water" means

This is the part most people miss. Official values count all water that enters your body:

plain water, still or sparkling
other drinks: tea, coffee, milk, juice, soft drinks
the water inside food, from fruit and vegetables to soup, yogurt and even bread

According to the National Academies, about 80% of total water comes from drinks and 20% from food. European estimates put the food share at roughly 20–30%. We go deeper into this in how much of your water comes from food.

So a 2.0-liter total for a woman in Europe means drinking about 1.4–1.6 liters, and the US figure of 2.7 liters means about 2.2 liters from drinks. For men: about 1.8–2 liters (EFSA) or 3 liters (US) from drinks.

The UK's NHS keeps it even simpler: it suggests 6 to 8 cups or glasses of fluid a day, and it says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count.

What changes how much you need

The official numbers describe an average person on an average day. Your own needs move up or down with:

Activity. Sweat losses during exercise can range from a few hundred milliliters to more than a liter per hour. A large study of more than 5,600 people found that physical activity explained more of the difference in water turnover than anything else (University of Wisconsin–Madison summary of the 2022 study in Science).
Heat and humidity. Hot weather increases sweating even at rest.
Body size. Bigger bodies turn over more water, though less than you might think: in the same study, 50 kg more body weight added only about 0.7 liters a day.
Pregnancy and breastfeeding. EFSA adds about 300 ml a day during pregnancy and about 700 ml while breastfeeding.
Illness. Fever, vomiting and diarrhea raise losses quickly.
Diet. Lots of fruit, vegetables and soup supply more water; a diet of dry, salty food supplies less.
Age. Older adults often feel less thirsty, so they may need a routine rather than relying on thirst alone.

Some health conditions work the other way. People with heart failure or certain kidney diseases are sometimes told to limit fluids. If you have a condition like that, follow your doctor's numbers, not a general guideline.

How to tell if you're drinking enough

You don't need a lab to check. Good everyday signals are:

You rarely feel thirsty. Thirst is a reliable signal for most healthy adults, though it gets weaker with age.
Your urine is pale yellow for most of the day. Dark yellow usually means you could drink more. See what your urine color says for the caveats (vitamins and some foods change the color).
You don't get the early signs of dehydration, such as a dry mouth, headache or unusual tiredness in the afternoon.

More water isn't always better. Drinking far beyond your needs in a short time can dilute the sodium in your blood, which is rare but serious. It mostly affects endurance athletes; read more in can you drink too much water.

A practical way to set your own goal

Start from a baseline. For most adults, 1.5–2 liters of drinks a day (women) or 2–2.5 liters (men) is a sensible start. If you prefer a personal number, estimate it from your weight; see how to calculate your water intake from body weight.
Add for sweat. On days you exercise or it's hot, add roughly 0.5–1 liter, more for long sessions.
Spread it out. A glass with each meal and one between meals already gets you to 6–7 glasses.
Check the signals for a week. Adjust up if you're often thirsty or your urine is dark, down if you're constantly running to the bathroom.

Tracking for a few days helps you see where you actually stand, because most people overestimate or underestimate their intake by a lot. Water Tracker suggests a daily goal from your weight and activity, lets you log a glass with one tap on your iPhone or Apple Watch, and sends reminders that go quiet once you've reached the goal. If you already use Apple Health, your drinks are saved there as Dietary Water.

Bottom line

Europe: 2.0 l (women) / 2.5 l (men) of total water a day. US: 2.7 l / 3.7 l.
Those totals include food, which provides around 20–30% of your water.
From drinks, most adults need roughly 1.5–3 liters, depending on sex, size, activity and climate.
Thirst and pale urine are good everyday guides. If you have a heart or kidney condition, or you're pregnant, ask your doctor.

This article is general information, not medical advice. If you have a health condition, are pregnant or take medication, ask your doctor how much you should drink.