How Many Galaxies Are There in the Universe?

The current best estimates put the number of galaxies in the observable universe between 200 billion and 2 trillion. The lower number comes from Hubble Deep Field counts; the higher number comes from a 2016 study extrapolating undetected dwarf galaxies. JWST observations since 2022 are gradually pulling the estimate back toward the lower end.

It's an enormous range — and it's still moving. Here's what's behind the count.

Where the 200 billion came from

In the 1990s, Hubble pointed at a tiny "blank" patch of sky for 100 hours and produced the Hubble Deep Field — an image full of more than 3,000 galaxies in a patch the size of a tennis ball at 100 meters. Multiplying that density across the entire sky gave around 200 billion galaxies.

That was the standard textbook number for two decades.

Where the 2 trillion came from

In 2016, a team led by Christopher Conselice at the University of Nottingham combined deep-field counts with simulations of how galaxy populations evolve over cosmic time. They argued there are 10× more small, faint galaxies in the early universe than telescopes can resolve.

That bumped the number to ~2 trillion. Many news headlines still cite that figure.

What JWST is finding

The James Webb Space Telescope can see galaxies as they were within 200 million years of the Big Bang. So far, JWST has confirmed that early galaxies are real, more numerous than expected, and surprisingly massive — but not as wildly overcounted as the 2 trillion estimate suggested.

A 2024 reanalysis using JWST data argued the actual number is closer to 200–300 billion. The discrepancy with the 2016 number comes from the fact that many of those "missing" small galaxies probably merged into bigger ones over cosmic time.

What "observable" actually means

The "observable universe" is everything close enough that light has had time to reach us in 13.8 billion years. The total universe is much bigger — possibly infinite. Outside the observable bubble there could be unbounded numbers of galaxies we will never see.

The observable universe is currently about 93 billion light-years in diameter. That's wider than the age × c because space itself has been expanding.

Each galaxy is its own city

The Milky Way alone holds 100 to 400 billion stars. Multiply that by 200 billion galaxies and you get roughly 2 × 10²² stars in the observable universe — about as many stars as there are grains of sand on every beach on Earth.

Add planets and the numbers stop being intuitive. The Kepler mission estimated at least one planet per star on average.

Why the count keeps changing

Three things keep shifting the estimate:

• Better telescopes resolve galaxies that were too faint before
• Better simulations reveal which structures are real galaxies vs star-forming gas clumps
• Mergers over time mean ancient galaxy counts don't equal modern ones

Whatever the exact number, "a lot" is the answer. Even the conservative 200 billion is mind-shaking.

What galaxies look like

About 60% are spirals like the Milky Way. About 15% are massive ellipticals — usually products of past mergers. The remaining 25% are irregulars, dwarfs, or peculiar shapes.

The biggest known galaxy, IC 1101, is roughly 50× the diameter of the Milky Way and contains about 100 trillion stars.

Want more cosmic-scale reads? Try how big is the universe or how black holes form.