How Much Water Should You Drink Per Day? What Experts Say

Hydration is critically important and dehydration, which occurs when your body loses more water than it takes in, can have many negative effects on your body. So, how much water should you aim to drink in a day? The Institute of Medicine of the National Academies recommends drinking 2.7 liters (or 91 ounces or 11 cups) for adult women a day, and 3.7 liters (or 125 ounces or 15 cups) for men^[2]Report Sets Dietary Intake Levels for Water, Salt, and Potassium To Maintain Health and Reduce Chronic Disease Risk. The National Academies of Science, Engineering, Medicine. Accessed 02/09/2022. .

It’s important to note this measurement accounts for total daily fluid rather than plain water. “According to the recommendations, about 20% of daily fluid intake can come from foods—think primarily water-rich vegetables and fruit—but also other foods and types of meals that are water rich,” says Wendy Bazilian, a registered doctor of public health and nutritionist and author of the Eat Clean, Stay Lean series. “Tea, coffee, milk and other beverages count, too.”

If you’re looking for a more individualized recommendation on how much water you should drink per day in ounces, Bazilian recommends calculating your fluid needs by your weight. “Aim to drink half an ounce for every pound of body weight,” she says. “In other words, divide what you weigh in half and aim to consume that many overall ounces of water daily from a variety of sources.” For example, if you weigh 150 pounds, aim to drink 75 ounces of water a day, which is around nine cups per day.

How Much Water Should Kids Drink Per Day?

The chart below from the Institute of Medicine of the National Academies also outlines how much water your child should drink per day, based on their age and sex.

Why Is There a Recommended Amount of Water Daily?

“The body uses and loses water daily, so it’s essential to replace water throughout the day,” says Sherri Hoyt, a registered dietitian nutritionist and an outpatient nutrition counselor at Missouri Baptist Medical Center in St. Louis, Missouri, stressing the importance of consistent hydration. “Water is lost during normal bodily processes, such as urination, bowel movements, sweating—even breathing. Aim to hydrate regularly throughout the day instead of all at one time or playing catch-up at the end of the day.”

To ensure you’re giving your body the necessary amount of hydration, be sure to get as close as possible to the daily recommendations for water intake. Below, read more about 10 important benefits of drinking enough water.

Heart Health

Cardiovascular disease is the top cause of death worldwide, but studies show that staying well-hydrated can reduce the risk of developing heart failure. This is because when you don’t drink enough water, your serum sodium levels increase, which in turn, causes the body to try and conserve water—a process known to contribute to heart failure.

Brain Health

Your brain contains about 73% water—even higher than the rest of your body—and needs lubrication to fire off all those hormones and neurotransmitters, Bazilian says. “According to a study published in the journal Nutrients, mild dehydration may interfere with brain activity and break down the ability to focus^[3]Benton D. (2011). Dehydration Influences Mood and Cognition: A Plausible Hypothesis? . Nutrients. 2011;3(5):555–573. .”

Kidney Health

Your kidneys may be small, but they’re important, as they remove waste and extra fluid from your body, which helps maintain the right balance of water, salt and minerals. “Water helps the kidneys remove waste from the blood and may prevent the formation of kidney stones,” says Hoyt.

Joint Health

As we age, it becomes increasingly important to keep our joints in good health, as many seniors have serious mobility issues. “Since joint cartilage is comprised of 80% water, staying well-hydrated can help cushion and lubricate joints,” Hoyt adds.

Healthy Weight Maintenance

A study in the Journal of Clinical Endocrinology and Metabolism found that something as simple as drinking enough water can increase your metabolism by as much as 30%, says Bazilian^[4]Boschmann M, Steiniger J, Hille U, Tank J, Adams F, Sharma AM, Jordan J. Water-Induced Thermogenesis. The Journal of Clinical Endocrinology & Metabolism. 2003;88(12), 6015–6019. . In the small study, participants saw this type of increase after drinking roughly 19 ounces of water, which is far less than the recommended daily amount.

Energy Levels

Feeling sluggish? When we’re not sufficiently hydrated, it hampers the flow of nutrients into our cells and clogs waste from flushing out, Bazilian says. This may cause fatigue to quickly set in, according to the Nutrition Review^[5]Popkin BM., D'Anci KE, Rosenberg IH. Water, hydration, and health. Nutrition reviews. 2010;68(8):439-458. .

Temperature Maintenance

Water is also crucial for body temperature maintenance. When there’s enough fluid traveling through your body, your bloodstream is better able to maintain a state of homeostasis in your body and keep your temperature at a steady 98.6 degrees Fahrenheit. “We are a body made of fat, muscle and other components,” says Bazilian. “If our temperature were to rise, the effect is fever. Sustaining a high body temperature over the long term can cause the body’s tissue composition to become altered.”

Mood Maintenance

As many of us can attest to, even the slightest drop below optimal hydration can make a person grouchy and irritable, according to research published in the Journal of Nutrition^[6]Armstrong LE, Ganio MS, Casa DJ, Lee EC,, Mcdermott BP, Klau JF, Lieberman HR. Mild Dehydration Affects Mood in Healthy Young Women. The Journal of Nutrition. 2011;142(2):382–388. . “Just a one to 2% water deficit—barely enough to feel thirsty—caused women in the study to fall into a foul mood, and they were more likely to experience headaches and fatigue,” Bazilian says.

Skin Health

Your skin is your body’s largest organ; and that means your skin needs its share of water, too. “Your skin is the outward barrier to the environment and helps transfer water in the form of sweat and also metabolic waste,” says Bazilian. “But if you don’t get adequate hydration, your skin will be forced to give up moisture to other, more critical bodily functions. Therefore, chronic dehydration can lead to dry, wrinkled skin.”

Immune System

No one wants to succumb to every virus that circulates, so to boost your immune system, raise your glass. “A healthy immune system may depend on your body staying adequately hydrated,” says Bazilian. “Constantly failing to get enough fluids into your body may depress the immune system and make it harder to fight off illnesses.”

Failing to get adequate hydration on a daily basis can be detrimental to just about every aspect of your health, while more severe dehydration is a medical emergency that requires immediate care, says Hoyt. “You may experience dizziness or lightheadedness. Without adequate water, blood volume decreases and blood pressure lowers, preventing the brain from getting enough blood.”

How to Tell If You’re Getting Enough Water

The best way to determine whether you’re getting enough fluid is to take a look at your urine. “If your urine is pale yellow like lemonade, you’re probably getting adequate hydration. But darker urine, like apple cider, can be an indication that you need to increase your fluid intake,” says Hoyt.

While it’s possible to drink too much water, it’s not a common occurrence. “This is not a concern for the average person,” says Hoyt. “Most often we see this in marathon runners or those engaging in endurance sports. When exercising for extended periods and with the loss of electrolytes through sweat, it’s important for these individuals to avoid over-hydrating with water.”

Drinking too much water at one time can cause diluted sodium levels in your body, a condition called hyponatremia. While there isn’t a specific amount of water you’d have to drink in order to cause hyponatremia, it’s a matter of taking in more water than your kidneys are able to process in a certain amount of time. This imbalance can lead to cerebral edema (swelling in the brain) in the most extreme cases, and confusion, nausea and headache in milder cases. To avoid hyponatremia, Hoyt recommends drinking less than one liter of water in an hour.