How many atoms are in a person?

By: Laurie L. Dove  | 
The human body is composed of billions of atoms.
How many atoms are inside you? And which elements do they comprise?
JGI/Blend Images/Thinkstock

Even if you have never landed a spot on "American Idol", you're a star. In fact, we all are. Nearly every atom within us was crafted billions of years ago by a star, but how many atoms are in the human body? Billions upon billions.

As stars burned, exploded, and eventually died, they created these basic elements that now appear in everything from stones and buildings to butterflies and humans. The exceptions to our star-based elemental origins are hydrogen atoms and other lightweight elements thought to have formed even earlier, at the very beginning of the universe [source: Tyson].


Here's a sense of scale to consider: Each of us is composed of more atoms than the Milky Way is composed of stars. And if you'd like to get more specific, this article will even share how you can roughly determine the number of atoms inside your own body.

The Atomic Composition of the Average Human Body

We're all made up of the same fundamental pieces of matter: atoms. Each atom contains three small subatomic particles -- protons, neutrons, and electrons. In the center of the atom, the protons and neutrons gather to form the nucleus, while the electrons zip around that nucleus as if they are minute planets orbiting their own little sun [source: Northwestern].

A human's body weighing 154 pounds (70 kilograms) is comprised of 7 billion billion billion atoms. To be clear, that's a 7 followed by 27 zeros! It includes a variety of different types of atoms -- only a few of which the average person is probably familiar with.


Of these atoms, three types make up the majority. Case in point? Ninety-nine percent of the atoms in human cells can be divided into the following amounts: 65 percent hydrogen, 24 percent oxygen, and 10 percent carbon. The remaining 1 percent of additional trace elements varies widely but usually includes zirconium, radium, boron, copper, and lead [sources: Freitas, Kross].

So How Many Atoms Do You Have?

Care to place a wager on the number of atoms in your own body? Such a bizarre piece of trivia could be yours to share, if you're ready to crunch some serious numbers. (Spoiler alert: the trivia won't be worth it!)

For example, you'll need to estimate the number of red blood cells in your body, as well as your number of skin cells, since all of these cells are loaded with atoms. Other areas of your genetic makeup may have more or fewer atoms, but this is a good place to start.


Since each cell has roughly the same number of atoms, your overall cell count factors in. So if you're a larger person, you'll have more atoms to count than if you're a smaller person. Another aspect to consider is your health. If you have specific health problems that have caused weight loss, muscle atrophy, or organ loss, that'll impact how many atoms you have.

It's also important to keep in mind that chemical processes can slightly alter these numbers. For instance, every breath of oxygen you take forms carbon dioxide, which when exhaled, recycles many of the same atoms back into the atmosphere. So don't worry about getting an exact number of how many atoms you have; you'll drive yourself crazy first!


A Mystery Beyond the Elements Listed

Despite the vast number of atoms in the human body, we are still surprisingly full of empty space. If all this empty space were squeezed out of the people who make up the human race, our bodies would become so compact that they could be contained in a box the size of a sugar cube.

Even more mind-blowing, the stars, planets and everything they contain, including humans, make up only 4 percent of the mass of the known universe. The remainder, scientists believe, is comprised of dark matter and dark energy, which are, as of yet, not well understood [source: Chown].


Lots More Information

Related Articles

  • Chown, Marcus. "Top 4 Bonkers Things About the Universe." Physics. (Aug. 6, 2014)
  • Freitas, Robert. "Nanomedicine." Foresight Institute. 1998. (Aug. 6, 2014)
  • Kross, Brian. "How Many Atoms Are In the Human Body?" Jefferson Lab. (Aug. 6, 2014)
  • Northwestern University. "What is an Atom?" (Aug. 6, 2014)
  • Tyson, Peter. "The Star in You." PBS. Dec. 2, 2010. (Aug. 6, 2014)