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Biology > Human Body Composition

The table below shows an estimate of the abundance of elements in the human body. The percentages are percent by mass of the indicated elements.

Element Symbol Atomic Number Percent in Universe Percent in Earth Percent in Human Body
Hydrogen H 1 91 0.14 9.5
Helium He 2 9 Trace Trace
Carbon C 6 0.02 0.03 18.5
Nitrogen N 7 0.04 Trace 3.3
Oxygen O 8 0.06 47 65
Sodium Na 11 Trace 2.8 0.2
Magnesium Mg 12 Trace 2.1 0.1
Phosphorus P 15 Trace 0.07 1
Sulfur S 16 Trace 0.03 0.3
Chlorine Cl 17 Trace 0.01 0.2
Potassium K 19 Trace 2.6 0.4
Calcium Ca 20 Trace 3.6 1.5
Iron Fe 26 Trace 5 Trace