High Quality Content by WIKIPEDIA articles! The composition of the human body can be looked at from the point of view of either mass composition, or atomic composition. To illustrate both views, the human body is ~70% water, and water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent. Thus, most of the mass of the human body is oxygen, but most of the atoms in the human body are hydrogen atoms. Both mass-composition and atomic composition figures are given below.