What percentage of body weight is water?
Up to 60% of the human adult body is water. According to H.H. Mitchell, Journal of Biological Chemistry 158, the brain and heart are composed of 73% water, and the lungs are about 83% water. The skin contains 64% water, muscles and kidneys are 79%, and even the bones are watery: 31%.
The average adult human body is 50-65% water, usually 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. It varies according to gender and fitness level because fatty tissue contains less water than lean tissue