What is the total number of atoms in a human body?

Even if you’ve never made it onto "American Idol," you’re still a star. In reality, we all are. Almost every atom in our bodies was forged billions of years ago within a star, but how many atoms make up the human body? Trillions upon trillions.

As stars burned, exploded, and eventually perished, they produced the fundamental elements that now exist in everything from rocks and structures to butterflies and humans. The only exceptions are hydrogen atoms and other light elements, believed to have formed at the universe’s inception [source: Tyson].

To put things into perspective: Every individual contains more atoms than there are stars in the Milky Way. For those curious about specifics, this article will also guide you on estimating the number of atoms within your own body.

The Atomic Composition of the Average Human Body

All of us are constructed from the same basic units of matter: atoms. Each atom consists of three tiny subatomic particles—protons, neutrons, and electrons. Protons and neutrons cluster at the center to form the nucleus, while electrons orbit around it like tiny planets circling their own miniature sun [source: Northwestern].

A human body weighing 154 pounds (70 kilograms) contains approximately 7 billion billion billion atoms. To clarify, that’s a 7 followed by 27 zeros! These atoms come in various types, many of which the average person may not recognize.

Among these atoms, three types dominate. Specifically, 99 percent of the atoms in human cells are divided as follows: 65 percent hydrogen, 24 percent oxygen, and 10 percent carbon. The remaining 1 percent consists of trace elements like zirconium, radium, boron, copper, and lead [sources: Freitas, Kross].

So How Many Atoms Do You Have?

Want to guess how many atoms are in your body? This quirky fact could be yours to share, but only if you’re prepared to tackle some heavy calculations. (Spoiler: It might not be worth the effort!)

For instance, you’ll need to calculate the number of red blood cells and skin cells in your body, as these cells are packed with atoms. Other parts of your genetic makeup may vary in atomic count, but this is a solid starting point.

Since every cell contains a similar number of atoms, your total cell count plays a role. Therefore, a larger individual will have more atoms than a smaller one. Additionally, your health status matters. Conditions causing weight loss, muscle atrophy, or organ loss will affect your atomic count.

It’s also worth noting that chemical processes can slightly change these numbers. For example, each breath you take converts oxygen into carbon dioxide, recycling many atoms back into the air. So, don’t stress over finding an exact atomic count—it’s a sure way to drive yourself mad!

A Mystery Beyond the Elements Listed

Despite the immense number of atoms in the human body, we are largely composed of empty space. If this space were removed from every person on Earth, our bodies would compress so tightly that they could fit into a container no larger than a sugar cube.

Even more astonishing, stars, planets, and everything within them, including humans, account for just 4 percent of the universe’s total mass. Scientists believe the remaining 96 percent is made up of dark matter and dark energy, which remain largely mysterious and poorly understood [source: Chown].