Though the actual average percentages of water in the human body vary by gender, age, and weight, one thing is consistent: Starting at birth, more than half of your body weight is composed of water.
The average percentage of body weight that is water will remain above 50 percent for most or all of your life, though it does decline over time.
Keep reading to learn how much of your body is water and where all this water is stored. You’ll also discover how water percentages change as you age, how your body uses all this water, and how to determine your body water percentage.
For the first few months of life, nearly three-fourths of your body weight is made up of water. That percentage starts to decline before you reach your first birthday, however.
The decreasing water percentage through the years is due in large part to having more body fat and less fat-free mass as you age. Fatty tissue contains less water than lean tissue, so your weight and body composition affect the percentage of water in your body.
The following charts represent the average total water in your body as a percentage of body weight, and the ideal range for good health.
Water as percentage of body weight in adults
|Adults||Ages 12 to 18||Ages 19 to 50||Ages 51 and older|
Water as percentage of body weight in infants and children
|Birth to 6 months||6 months to 1 year||1 to 12 years|
|Infants and children||average: 74%|
With all this water in your body, you may wonder where in your body it’s stored. The following table shows how much water resides in your organs, tissue, and other body parts.
|Body part||Water percentage|
|brain and heart||73%|
|muscles and kidneys||79%|
In addition, plasma (the liquid portion of blood) is about 90 percent water. Plasma helps carry blood cells, nutrients, and hormones throughout the body.
Water storage at the cellular level
No matter where it is in the body, water is stored in:
- intracellular fluid (ICF), the fluid within cells
- extracellular fluid (ECF), the fluid outside the cells
About two-thirds of the body’s water is within the cells, while the remaining third is in extracellular fluid. Minerals, including potassium and sodium, help maintain ICF and ECF balances.
Water is essential in every system and function of the body, and has many responsibilities. For example, water:
- is a building block of new cells and the key nutrient every cell relies on for survival
- metabolizes and transports proteins and carbohydrates from the food you eat to nourish your body
- helps the body flush waste, mainly through urine
- helps maintain a healthy body temperature through sweat and respiration when the temperature rises
- is part of the “shock absorber” system in the spine
- protects sensitive tissue
- is part of the fluid that surrounds and protects the brain and a baby in the womb
- is the main ingredient in saliva
- helps keep joints lubricated
To get the percentage of water in your body, assume 1 liter equals 1 kilogram and then divide your TBW by your weight. It’s a simplistic estimate, but it will give you an idea if you’re in a healthy range for percentage of water in your body.
Getting enough water depends on the food and beverages you consume each day. The ideal amount of water you should consume varies greatly, depending on factors such as age, weight, health, and activity level.
Your body naturally tries to maintain healthy water levels by excreting excess water in urine. The more water and fluids you drink, the more urine is produced in the kidneys.
If you don’t drink enough water, you won’t go to the bathroom as much because your body tries to conserve fluids and maintain an appropriate water level. Too little water consumption raises the risk of dehydration and possible harm to the body.
Calculating water consumption
To calculate how much water you should drink daily to maintain a healthy amount of water in your body, divide your weight in pounds by 2 and drink that amount in ounces.
For example, a 180-pound person should aim for 90 ounces of water, or about seven to eight 12-ounce glasses, each day.
Keep in mind that you can consume water in a variety of ways. A glass of orange juice is mostly water, for instance.
Be careful, though, because caffeinated beverages, such as coffee, tea, or certain sodas, can have a diuretic effect. You will still retain a lot of the water in those drinks, but the caffeine will make you urinate more often, so you’ll lose more fluid than you would drinking water.
Alcohol has also diuretic properties and isn’t a healthy way to reach your water-consumption goals.
Foods with lots of water
- strawberries and other berries
- oranges and other citrus fruits
- watermelon, cantaloupe, and other melons
- skim milk
Soups and broths are also mostly water, but look out for the calorie content and for high levels of sodium, which can make these options a little less healthy.
Dehydration and its accompanying health problems are particularly risky for people exercising or working in hot, humid weather.
Likewise, being physically active in dry heat means your perspiration will evaporate more quickly, speeding up the loss of fluids and making you more vulnerable to dehydration.
Chronic health problems, such as diabetes and kidney disease, increase your odds of dehydration because of increased urination. Even being sick with a cold can make you less likely to eat and drink as much as you normally do, putting you at risk for dehydration.
While thirst is certainly the most obvious sign of dehydration, your body is actually becoming dehydrated before you feel thirsty. Other symptoms of dehydration include:
- dark urine
- less-frequent urination
- dry mouth
Infants and young children experiencing dehydration may have those same symptoms, as well as dry diapers for a long period and crying without tears.
Risks of dehydration
The risks of dehydration are plentiful and serious:
- heat-related injuries, starting with cramps, but potentially leading to heat stroke
- urinary tract infections, kidney stones, and related illnesses
- seizures resulting from imbalances of sodium, potassium, and other electrolytes
- sudden drops in blood pressure, leading to fainting and falls or hypovolemic shock, a potentially life-threatening condition caused by abnormally low oxygen levels in the body
Though it’s unusual, it is possible to drink too much water, which can result in water intoxication, a condition in which levels of sodium, potassium, and other electrolytes become diluted.
If sodium levels fall too low, the result is hyponatremia, which can lead to several potentially serious health problems.
Certain medical conditions can make you more vulnerable to water intoxication, because they cause fluid retention in the body. So even drinking a normal amount of water may push your levels too high.
These conditions include:
The exact percentage of water in your body changes with age, weight gain or loss, and daily water consumption and water loss. You’re usually in a healthy range if your body water percentage is more than 50 percent throughout your life.
As long as you make water and fluid intake a part of your day — stepping up your consumption on hot days and when you’re exerting yourself physically — you should be able to maintain healthy fluid levels and avoid the potential health problems that come with dehydration.