We all know how important water is, but how much water is in the human body? Understanding that water is essential to our bodily functions is a key motivator for staying healthily hydrated. If we can begin to understand how all the different parts of our anatomy need water, we may find it easier to remember to drink enough fluid every day.
In this article, as well as revealing how much water is in the human body, we also take a look at how it’s distributed, and how each part uses water to function.
How much water is in the human body?
Over half of our bodies are made up of water. The actual amount of water in your body will depend on your weight, age and gender. As you age, your body water percentage will decrease.
At birth, around three quarters of our body weight is water. As we grow, our body fat increases and our lean tissue decreases. Fatty tissue contains less water. Therefore, over time, our weight and the amount of fatty tissue our bodies contain affects our body water percentage.
An average healthy male between the ages of 19 and 50 will have a body water percentage of around 60%, whereas an average healthy female in the same age range will have a body water percentage of around 50%.
From birth to six months, a baby’s body water percentage will be around 75%. From six months to 12 years, a child’s body water percentage will be around 60%. In teenage years, around 56% of a female’s body weight will be made up of water, compared to around 59% of a male’s. The average body water percentage for a female over 50 is 47%, whereas as male’s is 56%.
You can calculate how much water your own body contains by using the Watson formula:
Female formula
–2.097 + (0.1069 x height in cm) + (0.2466 x weight in kg) = total body water in litres
Male formula
2.447 – (0.09145 x age) + (0.1074 x height in cm) + (0.3362 x weight in kg) = total body water in litres
To then calculate how much that is as a percentage of your body weight, you simply divide your total body water by your weight (in kg) and multiply that answer by 100.
For example, a 1.62 metre high female weighing 55 kg:
-2.097 + (0.1069 x 162 cm = 17.3178) + (0.2466 x 55 kg = 13.563) = 28.7838 litres
28.7838 litres ÷ 55 kg x 100 = 52%
While this isn’t going to be precise, it serves to give a rough idea of how much water is in your body. A healthy range for females up to 50 is 41% to 60%, and for males up to 50 it’s 43% to 73%. For the over-50s, a healthy range for females is 39% to 57%, for males it’s 47% to 67%.
Why do we need water?
Water is one of the key ingredients of all the major parts that make up the human body:
- Plasma is around 92% water. Plasma is the liquid part of blood that carries around the red and white blood cells and platelets
- 83% of our lungs are water
- 79% of our muscles and kidneys are water
- Our brains and heart are 73% water
- 64% of our skin is water
- Our bones are 31% water
Everything in our body is made up of cells, and over 70% of each cell is made of water. Water is stored in intracellular fluid (the fluid within cells) as well as in extracellular fluid (the fluid outside cells). Water is everywhere in our bodies, and that’s why we need it so much.
What does water do for the body?
Here are the top ten little everyday miracles that water performs in our bodies to keep us in tip-top health:
- Water is the main nutrient every cell in our body needs to function. Cells are the building blocks of our bodies, they group together to form our tissues and organs.
- Water helps our brain function. Dehydration can adversely affect our concentration and ability to navigate complex tasks. We might also be prone to headaches or reduced alertness if we don’t drink enough water.
- Water aids digestion. It helps to break down the food we eat and then carries the proteins and carbohydrates around our body for fuel.
- Water flushes out our waste. Water helps our kidneys remove waste from our blood. We then pee out what our bodies don’t need.
- Water keeps our blood flowing. As the plasma in our blood is mostly water, we need to stay hydrated to stop our blood from becoming too concentrated. A lack of the electrolyte minerals naturally found in water, such as magnesium and potassium, affects the normal function of our hearts and muscles. Dehydration may also decrease our volume of blood, making us dizzy and light-headed.
- Water protects our sensitive bits. Our body tissue needs to stay moist, so when we don’t drink enough water, we begin to dry up. Our super sensitive eyes, nose and mouth all need to stay hydrated. Water is also part of the fluid around our brain that keeps it protected.
- Water is our built-in shock absorber. It’s part of our spinal cord’s protective system and also helps lubricate and cushion our joints.
- Water regulates our temperature. When we exercise, our muscles generate heat. To keep our temperature down, we get rid of that heat by sweating it out. Our bodies do the same in hot weather, and therefore need lots of water to be able to generate enough sweat and keep us cool.
- Water keeps our skin looking good. The outermost layer of our skin, the epidermis, will feel rough and lose its stretchiness if it doesn’t contain enough water
- Water keeps our mouths working. We naturally produce saliva to keep our mouths moist. As the saying ‘makes your mouth water’ suggests, the secretion of saliva anticipates digestion. It also protects our teeth and gums and helps prevent infections. Saliva is 99% water.
In this article, we’ve explained why water is so important to our everyday health. With over half our bodies being made up of water, we need to replace the fluid we’re naturally losing all the time.
It’s always best to replace like for like, so drinking plenty of pure water during the day will help us function properly. A great way to easily stay hydrated is to have a hot and cold water dispenser to hand that purifies your tap water, ensuring that it can be as tasty and healthy as possible.
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