Here's how many atoms are in the observable universe

Have you ever wondered how many atoms are in the observable universe? The math has been done, and here is the closest answer.

Published Mon, Jul 19 2021 4:04 AM CDT   |   Updated Mon, Aug 16 2021 10:55 PM CDT

The universe is constantly expanding, and at the moment, researchers believe that the observable universe has stretched 46 billion light-years from its beginning 13.8 billion years ago.

Here's how many atoms are in the observable universe 01 |

By measuring the cosmic microwave background radiation, researchers are able to quantify how fast the universe is expanding and thus its size, which are both key factors in figuring out how many atoms are in the observable universe. According to, there are a few assumptions to be made before the calculation can be made; all atoms are contained within stars (they aren't, but the majority of them are), and all of the atoms in the universe are hydrogen atoms (they aren't, but hydrogen atoms account for 90% of the total atoms in the universe).

Calculation: 10^11 to 10^12 galaxies in the observable universe, and each galaxy contains between 10^11 and 10^12 stars. That answer puts the total number of stars in the observable universe to be between 10^22 and 10^24. Now for weight. The average star weighs 2.2x10^32 pounds, which calculates the average mass of the universe to be around 2.2x10^55 pounds. Now that the mass of the universe has been found, we need to figure out how many atoms can fit inside of it. Each gram of matter contains around 10^24 protons, putting the average number of atoms in the observable universe to be 10^82.

Or -

10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 atoms.

It should be noted that the above number is not exact and is a rough approximation that contains assumptions to simplify the equation. For a more in-depth explanation for how this number arrived, check out this link here.

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Jak joined the TweakTown team in 2017 and has since reviewed 100s of new tech products and kept us informed daily on the latest science and space news. Jak's love for science, space, and technology, and, more specifically, PC gaming, began at 10 years old. It was the day his dad showed him how to play Age of Empires on an old Compaq PC. Ever since that day, Jak fell in love with games and the progression of the technology industry in all its forms. Instead of typical FPS, Jak holds a very special spot in his heart for RTS games.

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