How Many Atoms There Are in the Human Body

Atoms in the Body

Scientist analysing molecular model in laboratory

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Have you ever wondered how many atoms are in the human body? Here's the calculation and answer to the question.

Short Answer

There are approximately 7 x 1027 atoms in the average human body. This is the estimate for a 70 kg adult human male. Generally, a smaller person would contain fewer atoms; a larger person would contain more atoms.

Atoms in the Body

On average, 87 percent of the atoms in the body are hydrogen or oxygen. Carbon, hydrogen, nitrogen, and oxygen together account for 99 percent of the atoms in a person. There are 41 chemical elements found in most people. The exact number of atoms of the trace elements varies widely according to age, diet, and environmental factors. Some of these elements are needed for chemical processes in the body, but others (e.g., lead, uranium, radium) have no known function or are toxic contaminants. Low levels of these elements are a natural part of the environment and typically do not cause health problems. In addition to the elements listed in the table, additional trace elements may be found in some individuals.

Reference: Freitas, Robert A., Jr., Nanomedicine, http://www.foresight.org/Nanomedicine/index.html, 2006.

Atomic Composition of a Lean 70-kg Man

Element # of Atoms
hydrogen 4.22 x 1027
oxygen 1.61 x 1027
carbon 8.03 x 1026
nitrogen 3.9 x 1025
calcium 1.6 x 1025
phosphorus 9.6 x 1024
sulfur 2.6 x 1024
sodium 2.5 x 1024
potassium 2.2 x 1024
chlorine 1.6 x 1024
magnesium 4.7 x 1023
silicon 3.9 x 1023
fluorine 8.3 x 1022
iron 4.5 x 1022
zinc 2.1 x 1022
rubidium 2.2 x 1021
strontium 2.2 x 1021
bromine 2 x 1021
aluminum 1 x 1021
copper 7 x 1020
lead 3 x 1020
cadmium 3 x 1020
boron 2 x 1020
manganese 1 x 1020
nickel 1 x 1020
lithium 1 x 1020
barium 8 x 1019
iodine 5 x 1019
tin 4 x 1019
gold 2 x 1019
zirconium 2 x 1019
cobalt 2 x 1019
cesium 7 x 1018
mercury 6 x 1018
arsenic 6 x 1018
chromium 6 x 1018
molybdenum 3 x 1018
selenium 3 x 1018
beryllium 3 x 1018
vanadium 8 x 1017
uranium 2 x 1017
radium 8 x 1010