Most of the human body is water, with an average of roughly 60%. The amount of water in the body changes slightly with age, sex, and hydration levels.
For example, babies have a high percentage of water in their bodies, which decreases with age.
Also, fatty tissue contains less water than muscle, so the percentage of water can vary with body type.
Water is essential for health and is necessary for numerous bodily functions. These include:
- temperature regulation
- cellular function
- waste removal
People can maintain the balance of water in their bodies by drinking fluids throughout the day. They may need to drink more water after exercise and in hot weather.
This article will discuss the percentage of water in the human body, why it varies, and why it is important.
The percentage of water in the body varies slightly, depending on factors such as age and sex, but is usually within the 45–75% range.
There is more water in lean muscle than there is in fatty tissue.
Typically, a female body contains a lower percentage of water than a male one. This is due to females having a higher percentage of fat.
This water distribution means that people with a higher percentage of body fat are likely to have a lower percentage of water in their bodies.
The percentage of water in the body changes with age. Babies have a very high percentage of water in their bodies, while older adults have less.
The following tables give the average percentages and ranges of water in the body, according to sex and age:
|Age 12–18 years||Age 19–50 years||Age 51 years and older|
|Birth to 6 months||6 months to 1 year||1–12 years|
|Infants and children||Average: 74%|
Body size, shape, and balance of muscle and fat can all affect the percentage of water in a person’s body.
Some organs contain much more water than others. The brain and kidneys possess the highest percentage of water; the bones and teeth contain the lowest proportion.
|Body part||Water percentage|
Regardless of water content, all parts of the body need water to work properly.
Drinking enough water every day is crucial to health and plays a part in almost all body functions. An older review states that water is the most important nutrient in the body.
Water is essential in areas such as:
- protecting the spinal cord and other sensitive tissues
- removing waste by urination, sweating, and bowel movements
- regulating temperature
- lubricating and cushioning joints
There is a range of scientific methods to calculate body composition, including the percentage of water.
People can use online calculators to determine the percentage of water in the body.
They can also use the Watson formula to calculate total body water in liters.
Watson formula for males
2.447 – (0.09156 x age) + (0.1074 x height in centimeters) + (0.3362 x weight in kilograms) = total body weight (TBW) in liters.
Watson formula for females
–2.097 + (0.1069 x height in centimeters) + (0.2466 x weight in kilograms) = total body weight (TBW) in liters.
To get the percentage of body water, people can assume 1 liter equals 1 kilogram and then divide TBW by weight. This can provide a rough estimate of whether a person is in a healthy range for percentage of body weight.
It is essential to drink enough water to support all functions of the body. Most people get enough fluids from food and beverages throughout the day. They should always drink more fluids in hot weather or after exercise.
The Centers for Disease Control and Prevention (CDC) also recommend:
- carrying a water bottle for easy access
- choosing water instead of sugar-sweetened beverages
- choosing water when eating a meal out
- adding a wedge of lemon or lime to water to improve taste
Some tips for older adults specifically include:
- not waiting until feeling thirst to drink fluids
- drinking a glass of water before and after exercise
- taking a sip of water between each bite of food at meals
- drinking a full glass of water when taking medication
There is no set daily amount of fluid that a person should drink. The amount varies, depending on age, sex, weight, health, physical activity, and the climate where a person lives.
As an approximate guide, the minimum fluid intake is as follows:
|Age||Recommended fluid intake (milliliters per day)|
|9–13 years (males)||2,400|
|9–13 years (females)||2,100|
|14–18 years (males)||3,300|
|14–18 years (females)||2,300|
Dehydration is more likely in a warmer climate or hot weather. A person should always make sure to drink extra fluids in the heat.
Similarly, exercise can cause dehydration because the body uses more fluid and loses water through sweat.
Older adults may gradually lose some of their sense of thirst. A good rule of thumb is to drink fluids throughout the day. Once a person feels thirsty, they may already be slightly dehydrated.
Water toxicity happens when there is too much water in the body. This can dilute essential electrolytes in the blood, cause cells to swell, and put pressure on the brain.
Drinking too much water is difficult. There have been cases of water poisoning in people who drank a lot of water in a very short space of time. This may be during endurance sports because of heat stress, or when using recreational drugs that increase thirst.
There is no clear limit for drinking too much water. The kidneys can remove 20–28 liters of water per day, but they cannot excrete more than 0.8 to 1.0 liters per hour. Drinking more than this can be harmful.
A majority of the human body consists of water. The percentage varies with age, sex, and body type but is usually around 60%. A person can maintain the balance of water in the body by taking in enough fluids during the day.
Water is crucial to keep the body working correctly. It is present in the blood, skin, organs, and bones. There is water in every cell of the body, from the brain to the teeth.