Have you ever wondered how much of your body is water? The percentage of water varies according to your age and gender. Here's a look at how much water is inside you. The amount of water in the human body ranges from 50-75%. The average adult human body is 50-65% water, averaging around 57-60%. The percentage of water in infants is much higher, typically around 75-78% water, dropping to 65% by one year of age.