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Key takeaways
The average adult is advised to follow the “8×8” rule, which suggests drinking eight, 8-ounce glasses of water a day, though individual needs may vary based on factors like activity level and climate.
Water consumption impacts brain function, muscle and organ health, waste removal, skin elasticity, and supports the immune system by aiding in toxin removal and nutrient absorption.
Factors including age, gender, physical activity, climate, pregnancy, and breastfeeding significantly influence daily water intake needs, with recommendations adjusting accordingly.
Symptoms of dehydration range from physical signs like thirst, dizziness, and dark urine to cognitive and emotional issues such as mood swings and lack of mental clarity, highlighting the importance of adequate hydration.
Adequate water intake can impact the entire body. Brain function, muscles, organs, waste removal, and skin elasticity are all affected by the amount of water an individual consumes. In addition, water helps regulate body temperature and majorly contributes to the absorption of vitamins and nutrients as part of the digestive process. Weight loss is another important benefit of drinking water. Drinking water can also help remove toxins from the body and keep the immune system strong.
Now that you know why water is important, let’s dive into how much water you should drink daily.
How much water should you really drink in a day?
Throughout the day, the body continually loses fluids through perspiration, urination, and even respiration. Like nutrition, hydration needs vary from person to person. Age, gender, activity levels, environment, diet, metabolism, and overall health contribute to calculating, “How much water should I really drink in a day?”
The “8×8” rule explained
The “8×8” rule was a suggested daily intake (for the average adult) of eight, 8-ounce glasses of water (a total of 64 ounces, almost 2 liters, throughout the day). This goal may be more or less than what some individuals need, depending on exercise, activity level, and exposure to hot climates. Modern research suggests a “drink to thirst” strategy, which involves consuming more fluids if there are signs of dehydration, such as infrequent or dark urine.
Body size contributes to how much water one should drink, so if you’re looking for an approximate number of ounces of fluid intake, there’s another “rule” to consider. The equation is simple: half of your body weight equals the number of ounces recommended to drink per day. A healthy adult weighing 160 pounds divides that number by two to get the number 80. A good approximation of fluid needs for that individual is 80 ounces of water daily.
While this formula may be applied to the average person, athletes need a much higher amount of fluids to stay hydrated. In fact, a 1:1 ratio of body weight to ounces of water per day is suggested to determine the amount of fluid needed for athletes. Therefore, if an athlete weighs 150 pounds, the total water intake should also be about 150 ounces for the day.
Factors that affect water consumption needs
Consider age and gender
Water consumption is not one size fits all. Age and gender should be taken into consideration when calculating your fluid intake. Generally, men need more water than women, and children need less water than adults. Fortunately, the formula of half of one’s body weight equaling an approximate number of ounces of water to drink daily applies to men, women, and children. If a child weighs 50 pounds, then approximately 25 ounces of water are recommended daily for that child. These numbers vary from individual to individual.
The American Academy of Pediatrics suggests that infants of about 6 months of age can begin to drink 4 to 8 ounces of water per day to stay hydrated. Below is a chart that further describes how much liquid children should drink based on their age.
| Age | Cups of beverages (water, milk or juice) per day* |
| 6 months – 1 year | ½ to 1 cup |
| 1-3 years | 4 cups |
| 4-8 years | 5 cups |
| 8+ years | 7-8 cups |
*May vary by person depending on factors such as activity level, heat, and humidity.
Remember, other foods and fluids contribute to hydration needs. Look for signs of dehydration, and be sure to drink extra water during prolonged exercise or high-heat situations.
Older adults are at a higher risk for potential long-term damage to the body and brain if they experience severe dehydration. Lacking enough fluids can cause memory loss and confusion associated with dementia in an aging brain. If severely dehydrated, aging populations are more susceptible to urinary tract infections, kidney stones, kidney failure, and other serious health conditions. Older people, especially those who take medication, should consult their healthcare providers about their individual water intake needs.
Physical activity levels
Another factor to consider when determining how much water to drink is one’s level of physical activity. Energy expenditure, such as exercise, employment, and lifestyle, all play a role in fluid consumption. For example, if you are a landscaper and it is hot outside, the need to drink extra water is greater than someone working at a computer in an air-conditioned office. Increased activity levels equal an increased need to hydrate.
Perspiration and respiration greatly contribute to the loss of bodily fluids. You should intentionally drink before, during, and after a high-intensity workout. Drinking excess water up to two hours or more prior to exercising can help prepare the body for fluid loss through sweating. Consuming water every 15 to 20 minutes while working out will safely keep you hydrated. Following exercise, more water or an electrolyte beverage can ensure that all fluids have been restored and prevent dehydration. A good indicator that fluid levels are healthy is by assessing urine color. Urine should be a light or pale yellow.
Climate and weather conditions
The weather and climate can affect your hydration status. You can anticipate needing to drink additional water if you are exposed to hot or dry climates. Remember to take plenty of water on outings, such as hiking and biking, especially in remote areas.
While the need to stay hydrated on hot summer days may seem obvious, other weather conditions and elevation can play a role in how our bodies need to replenish liquids. In colder winter months, the body needs to stay hydrated to keep warm. Hot tea and brothy soups are a great way to stay warm and hydrated. Even elevation can affect the need to drink water. In general, people may need to hydrate more when living at higher elevations.
Pregnancy and breastfeeding
It is a common recommendation for women to increase water consumption during pregnancy. Drinking additional water supports the increase of blood volume along with amniotic fluid and fetal circulation. Furthermore, drinking water can help relieve pregnancy-related constipation. The risk of constipation increases for a variety of reasons, including taking iron supplements, which is suggested for most pregnancies.
Tara Daystar, a lactation consultant and founder of Roots Midwifery, suggests that there is a need to increase water consumption while pregnant. She advises, “Drink to thirst is a good practice as the body will naturally let you know if you need to hydrate.” Daystar reinforces that looking for signs of dehydration, such as dark urine, and consult your doctor or healthcare provider about your specific needs while pregnant or breastfeeding.
A breastfeeding mother should continue to drink extra fluids to stay hydrated. While increased fluids do not equate to increased milk supply, milk production can become more difficult if a nursing mom becomes dehydrated. Some mothers get in the habit of enjoying a glass of water while they nurse their babies. When breastfeeding, the body releases oxytocin, which stimulates thirst in order to encourage the body to replenish lost fluids.
Symptoms of dehydration
Not drinking enough water can lead to dehydration. Dehydration occurs when the body loses more fluids than it has replaced. Insufficient water consumption, physical activity, extreme heat, and certain medications can contribute to becoming dehydrated. Health problems, such as shock, brain swelling, kidney failure, and seizures, are just some of the concerns of severe dehydration.
Physical signs and symptoms of dehydration
Not drinking enough fluid can lead to serious health risks. It is important to know the physical signs of dehydration. Treating dehydration early is simple and reduces the need for medical intervention or damage to the body or brain. Signs and symptoms of dehydration may include:
- Thirst
- Tiredness
- Feeling light-headed
- Dizziness
- Headache
- Infrequent urination (less than three to four times throughout the day)
- Dark urine
- Dry mouth and lips
- Dry cough
- Shortness of breath
- Increased or high blood pressure
- Red skin
- Loss of appetite
- Chills
- Clammy skin
- Swollen feet
- Cramping in legs, stomach, and hands
Being aware of the signs of dehydration can prevent an emergency situation for you or someone else.
Cognitive and emotional symptoms of dehydration
While the physical symptoms of dehydration are often more noticeable, it is also beneficial to be aware of the emotional and cognitive problems associated with lack of proper hydration. When the body is dehydrated, the brain cells can actually shrink, creating distress and damage to cognitive functions. Cognitive and emotional signs that correspond with dehydration may include:
- Mood swings
- Lack of mental clarity or “brain fog”
- Short-term memory loss
- Confusion
- Inability to focus
- Brain swelling
Drinking water throughout the school or work day could help you stay focused and energized. Offering and providing water to older adults or patients struggling with memory loss could help improve their cognitive function.
Hydration tips
Most experts suggest drinking plain water as the best way to stay hydrated. Water has zero calories and is usually readily available via tap. Herbal teas and fruit juices are other healthy choices that can help meet daily fluid intake goals. Surprisingly, almost any beverage, even soft drinks, milk, and coffee, contributes to the body’s replenishment of liquids. Milk provides calcium-rich nutrients when hydrating, especially for young children. Soda is a sugary drink with no added health benefits but can provide mild hydration. Although coffee is considered a diuretic and can cause the body to expel excess fluid, it is not significant enough to cause dehydration in most cases. Alcohol, on the other hand, is dehydrating and should be avoided.
Electrolytes
Sports or energy drinks with electrolytes can be beneficial to prevent dehydration or recover from it. A more natural option for electrolyte replacement is coconut water. Either way, these beverages usually contain the potassium, sodium, manganese, and calcium needed to replace necessary minerals that are often lost through perspiration.
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Water-dense foods
An easy way to get more fluids in your diet is by adding more water-dense foods, such as fruit, into your meals or snacks. Watermelon, tomatoes, oranges, and cucumbers have a high percentage of water and can help keep you hydrated. Soups are also made of a significant amount of water. Eating stew or soup broth is a great way to maintain fluids, especially in the winter. Also, many people enjoy a freshly squeezed lemon or splash of fruit juice in their water to add variety.
Hydration technology
Technology can also play a role in staying hydrated. Whether you want to track how much water you drink in a day or just have a reminder to drink more, technology can help.
- Set a timer on your phone to remind you to drink water throughout the day
- Download an app that reminds you to drink water
- Use a Bluetooth water bottle that reminds you to drink water
- Get fun, motivational water bottles
- Track water intake on an activity tracker, smartwatch, or phone
Getting enough fluids is important for optimal health and can lead to clearer skin and weight loss. Everyone is unique in their hydration needs. While some individuals will just “drink to thirst,” others may calculate each ounce of water consumed with a tracking app. Preventing dehydration is key, no matter which route you choose. Signs of dehydration, such as feeling overheated, dark urine, red skin, headache, or even a shift in your mood, maybe your body telling you it’s time to drink more water.