---
title: "How many planets are there in the galaxy? at least 100 billion"
description: "at least 100 billion — probably more planets than stars How the figure is estimated, how confident it is, and what makes the scale graspable."
url: https://atoneplace.net/how-many/planets-in-the-milky-way/
site: "At One Place"
---

# How many planets are there in the galaxy?

**How many planets are there in the galaxy?: at least 100 billion — probably more planets than stars**

Kepler stared at about 150,000 stars in one patch of sky for four years and found around 2,700 planets. Everything we say about 100 billion planets rests on correcting that sample for what it could not have seen.

Statistically corrected results from the Kepler mission imply that the average star hosts at least one planet, so the Milky Way contains at least as many planets as stars — over 100 billion. Small planets are far more common than large ones, and red dwarfs, the most numerous stars, appear to host compact multi-planet systems routinely. Roughly 6,000 exoplanets have actually been confirmed, so the 100 billion is entirely an extrapolation from a heavily biased sample. Free-floating planets bound to no star may add a comparable number again.

## How the figure is arrived at

Transit surveys detect a planet only if its orbit is edge-on to us, which is a few percent of the time for a close orbit and far less for a distant one, and only if the dip in brightness is above the noise. Divide the detections by that geometric and sensitivity probability and you recover the true occurrence rate. Microlensing surveys catch wide orbits that transits miss and support the same conclusion.

## How confident it is

- **Low estimate:** 100,000,000,000
- **High estimate:** 400,000,000,000
- **Spread:** 4.0× between the bounds

## Other space and the universe counts

- [How many stars are there in the universe?](https://atoneplace.net/how-many/stars-in-the-universe/) — about 200 billion trillion
- [How many stars are there in the Milky Way?](https://atoneplace.net/how-many/stars-in-the-milky-way/) — between 100 billion and 400 billion
- [How many atoms are there in the universe?](https://atoneplace.net/how-many/atoms-in-the-universe/) — about 10^80
- [How many galaxies are there?](https://atoneplace.net/how-many/galaxies-in-the-universe/) — hundreds of billions — possibly 2 trillion
- [How many satellites are in orbit?](https://atoneplace.net/how-many/satellites-in-orbit/) — about 12,000 active satellites
- [How many moons are there in the solar system?](https://atoneplace.net/how-many/moons-in-the-solar-system/) — about 900 confirmed, and the number keeps moving
- [How many stars can you see with the naked eye?](https://atoneplace.net/how-many/stars-visible-to-the-naked-eye/) — about 9,000 over the whole sky; roughly 2,500 at once
- [How many constellations are there?](https://atoneplace.net/how-many/constellations/) — exactly 88
- [How much space junk is there?](https://atoneplace.net/how-many/space-debris/) — about 40,000 tracked objects, and over 130 million fragments too small to track
- [How many asteroids are there?](https://atoneplace.net/how-many/known-asteroids/) — about 1.4 million catalogued

## Common questions

### How many planets are there in the galaxy?

at least 100 billion — probably more planets than stars

### How is that estimated?

Transit surveys detect a planet only if its orbit is edge-on to us, which is a few percent of the time for a close orbit and far less for a distant one, and only if the dip in brightness is above the noise. Divide the detections by that geometric and sensitivity probability and you recover the true occurrence rate. Microlensing surveys catch wide orbits that transits miss and support the same conclusion.

## Related pages

- [How many stars are there in the universe?](https://atoneplace.net/how-many/stars-in-the-universe/)
- [How many stars are there in the Milky Way?](https://atoneplace.net/how-many/stars-in-the-milky-way/)
- [How many atoms are there in the universe?](https://atoneplace.net/how-many/atoms-in-the-universe/)
- [How many galaxies are there?](https://atoneplace.net/how-many/galaxies-in-the-universe/)
- [How many satellites are in orbit?](https://atoneplace.net/how-many/satellites-in-orbit/)
- [How many moons are there in the solar system?](https://atoneplace.net/how-many/moons-in-the-solar-system/)
- [How many stars can you see with the naked eye?](https://atoneplace.net/how-many/stars-visible-to-the-naked-eye/)
- [How many constellations are there?](https://atoneplace.net/how-many/constellations/)
- [How many people are there in the world?](https://atoneplace.net/how-many/people-alive-right-now/)
- [How many countries are there in the world?](https://atoneplace.net/how-many/countries/)
- [How many bones are in the human body?](https://atoneplace.net/how-many/bones-in-the-human-body/)
- [How many grains of sand are there on Earth?](https://atoneplace.net/how-many/grains-of-sand-on-earth/)
- [How many ants are there in the world?](https://atoneplace.net/how-many/ants-on-earth/)
- [How many trees are there in the world?](https://atoneplace.net/how-many/trees-on-earth/)

## Sources

- NASA — National Aeronautics and Space Administration (https://www.nasa.gov/) [Public domain (US Government)]