How Many Atoms Does the Human Body Contain?

There are about 7 octillion atoms in the adult human body. The number of atoms in the human body is never constant, but an estimate can be calculated based on the average weight of a human adult and the average mass of an atom. An average human weighs 70 kilograms (about 154 pounds) and the average mass of an atom is a thousandth of a trillion of a trillion of 1 kilogram (0 followed by 27 decimal places). The calculation results in 7 octillion atoms or a 7 followed by 27 zeroes.

More about the human body:

• Atoms are the smallest and most basic units of matter, made up of protons, electrons and neutrons.
• 99% of the human body is made up of hydrogen, oxygen and carbon.
• The number of atoms in the human body is more than 100,000 times the number of known stars in the universe.