The human body is approximately 99% comprised by mass of just six elements : Oxygen, hydrogen, nitrogen, carbon, calcium, and phosphorus.
Another five elements make up about 0.85% of the remaining mass: sulfur, potassium, sodium, chlorine, and magnesium.
The remaining 0.15% of the human body is comprised of 50 trace elements.
Most of the oxygen present is found in the form of water.
Below is the table of the approximate mass percentage of each element (excluding the trace elements) :