Medically reviewed by Adrienne Seitz, MS, RD, LDN, Nutrition — Written by Markus MacGill — Updated on November 17, 2021

People often hear that they should drink eight glasses of water per day. However, that may not be entirely true, and the amount of water a person should drink can vary depending on their age, activity level, & more.

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Water is an essential part of life, but how much should a person really be drinking?

The commonly touted wisdom of eight glasses of water per day may be suitable for some people, but it is not a “one-size-fits-all” recommendation.

Some experts say there is a lack of scientific evidence supporting these claims. Others cảnh báo that promoters include bottled water manufacturers.

So, how much water does a person really need? Read more to learn how much water khổng lồ drink, where khổng lồ get it, và the risks of drinking too little or too much.

Recommended daily water intake

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Back in 1945, the U.S. Food and Nutrition Board advised people khổng lồ consume 2.5 liters, or 84.5 fluid ounces (fl oz), of water per day, including fluid from prepared foods. Today, the Centers for Disease Control & Prevention (CDC) say there is no recommendation for how much plain water adults should consume daily.

The 2015–2020 U.S. Dietary Guidelines bởi not recommend a specific daily water or fluid intake, but they vì recommend choosing plain rather than flavored water & juices.

In the United Kingdom, the National Health Service (NHS) recommends consuming 6–8 glasses of water a day, or 1.9 liters (almost 65 fl oz), including water that is in food. The NHS notes this amount is suitable for a temperate climate. It says more will be needed in hotter climates.

Recommended intake by age

There is no fixed amount of fluid recommended by age, but some patterns emerge among healthy individuals doing a moderate amount of activity in a temperate climate.

The following sections show the average water intake for people of different ages.


Experts vì chưng not recommend plain water for infants before the age of 6 months.

The CDC says that if infants over 6 months of age need additional fluid on hot days, they can consume water in a bottle. However, their primary form of fluid and calories should be breast milk or formula.

Children over 12 months of age

Children over 12 months of age should be encouraged khổng lồ drink water in the following situations:

as part of their daily routine (for example, after brushing their teeth và before, during, & after playtime at school)when the weather is warmas an alternative to lớn sweetened drinks and juices

Children should limit their juice consumption to lớn one glass per day.

Parents are advised to lớn keep a pitcher handy to lớn encourage healthy water-drinking habits, and schools should have water fountains or equivalent facilities.

Adults ages 19–30 years

The recommended adequate intakes of total water from all sources each day for most adults between 19 & 30 years of age are:

3.7 liters (or about 130 fl oz) for men2.7 liters (about 95 fl oz) for women

People who are pregnant are likely lớn need an extra 0.3 liters (10 fl oz). Those who are breastfeeding will need an additional 0.7 to 1.1 liters (23–37 fl oz).

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Older adults

Older adults may be at risk of dehydration due to health conditions, medications, loss of muscle mass, reduction in kidney function, and other factors.

Older adults who are well hydrated have been found khổng lồ have:

fewer falls

Dehydration has been linked to a higher frequency of:

confusionkidney failureslower wound healing
Water nội dung as a percentage (%)Food or drink
90–99%fat-free milk, tea, coffee, juicy fruits (e.g., strawberries và cantaloupes), vegetables such as lettuce, celery, and spinach
80–89%fruit juice, yogurt, fruits such as apples, pears, & oranges, vegetables such as carrots and cooked broccoli
70–79%bananas, avocados, baked potatoes, cottage cheese
60–69%pasta, beans, peas, fish, chicken breasts, ice cream
30–39%bread, bagels, cheddar cheese
1–9%nuts, chocolate, cookies, crackers, cereals
0%oils, sugars

During exercise, people may need to consume more water than usual. The amount they should drink depends on:

the type and intensity of the activityenvironmental factors, such as temperaturethe form size and muscle mass of the individual

Older guidance from the American College of Sports Medicine (ACSM) advises drinking water during activity to prevent dehydration that leads lớn a decline in body toàn thân weight of more than 2 percent and changes in electrolyte balance.

These changes, researchers say, can lead lớn reduced performance.

However, a study published in the International Journal of Exercise Science concludes that a loss of up khổng lồ 4 percent of water has no effect on real-world sports performance.

This means that, while it is important to be hydrated before a workout — và a person should aim to lớn replace fluid lost after exercise — drinking water during a workout may not be essential. However, if people exercise for long periods, they may benefit from consuming water or an electrolyte beverage.

When should a person drink water?

Most of the time, the body’s sensitive natural mechanisms maintain appropriate fluid levels.

There are two main ways the body toàn thân does this: (1) through thirst, which tells a person to drink more water; và (2) through urine output, in which the kidneys regulate the water we consume by either emptying it into the urinary bladder or holding onto it in the blood plasma.

The kidneys also regulate the balance of electrolytes, such as sodium và potassium, in the toàn thân fluids. Additionally, they receive hormonal signals to conserve or release water into the urine if the brain detects changes in the concentration of the solutes in the blood.

It is often said that people need to drink at least eight 8-ounce (oz) glasses of water per day. However, this is an overly simplistic answer khổng lồ a complicated question.

The body toàn thân is good at regulating itself, và water is no exception. The body is constantly working to maintain a balance of water coming in và water going out. If a person drinks too much water, the body will excrete more. If they drink too little, it will excrete less.

In addition to body size và activity level, other everyday factors can play a role in determining how much water a person should drink.

For example, consuming more sodium & protein means a person may need lớn drink more water. Conversely, eating a lot of fruits và vegetables means they may not need to drink as much.

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Most of the time, the body toàn thân will give a person cues that tell them khổng lồ drink more or less fluid. The body even has a water-regulating hormone — arginine vasopressin — that manages thirst, fluid excretion, & the body’s water balance.