Have you ever wondered how much water is in the human body? The average amount of water ranges from 45-75%, but it varies according to age, gender, and health. Here’s a look at how much water is inside a person.
The average human is about 60% water. This is approximately 45 kg (100 lb) of water for the average adult.
Amount of Water in the Body
Babies and children contain the highest percentage of water. A newborn averages about 74% water (64% to 84%), while a 12-year-old averages about 60% water (49% to 75%). The average adult male is about 60% water, while the average adult female is 55% water. Women naturally have more fatty tissue than men, resulting in a lower percentage of water. An overweight person has a lower percentage of body water than a lean person. Elderly people may have slightly less water than when they were younger because they are more susceptible to dehydration. The average male over age 51 is about 56% water, while the average female of the same age is about 47% water. Feeling thirsty means you’ve already lost 2-3% of your body’s water.
|Average Percent Water||Average Weight (U.S.)||Water Weight (kg)||Water Weight (lbs)|
|Newborn||74%||3.5 kg (7.5 lb)||2.6 kg||5.5 lb|
|12 year old child||60%||41.5 kg (91.5 lb)||24.9 kg||54.9 lb|
|Adult male||60% (range: 43-73%)||76.4 kg (168.4 lb)||45.8 kg||101.0 lb|
|Adult female||55% (range: 41-60%)||88.8 kg (195.8 lb)||48.8 kg||107.7 lb|
|51 year old male||56%||88.3 kg (194.7 lb)||49.4 kg||109.0 lb|
|51 year old female||47%||75.5 kg (166.5 lb)||35.5 kg||78.3 lb|
Where Is Water in the Body?
About two-thirds of the body’s water is inside cells (intracellular fluid), while one-third is outside of cells (extracellular fluid). About 20% of the body’s water is in blood plasma.
The amount of water varies in different organs. As you might expect, bones contain a relatively low amount of water (31%). The skin is 64% water. The muscles and kidneys are 70% water. The human brain and heart are each 73% water. The lungs are the organ with the highest percentage of water (79%).
Functions of Water in the Human Body
Water is essential for life because it serves so many functions. Here are some of the body’s uses of water:
- Water is the primary building block of cells.
- It’s also a building block of important molecules, such as hormones and neurotransmitters.
- It acts as an insulator, regulating internal body temperature. This is partly because water has a high specific heat, plus the body uses perspiration and respiration to regulate temperature.
- Water keeps membranes moist. It helps keep the eyes clean and hydrated, is essential for the senses of smell and taste, makes it possible to swallow food and excrete feces.
- Water is needed to metabolize proteins and carbohydrates used as food. It is the primary component of saliva, used to digest carbohydrates and aid in swallowing food.
- The compound lubricates joints.
- Water insulates the brain, spinal cord, organs, and fetus. It acts as a shock absorber.
- Water flushes waste and toxins from the body via urine and perspiration.
- Water is the principal solvent in the body. It dissolves minerals, soluble vitamins, and certain nutrients.
- Water carries oxygen and nutrients to cells.
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