How Many Stars Are in the Universe?
The short answer everyone repeats is about 200 sextillion — that’s a 2 followed by 23 zeros, or 2 × 1023. The honest answer is that nobody knows, the real figure is a range from 1022 to 1024, and even that only counts the part of the universe we can see.
Both numbers are real estimates with real disagreement behind them. Slide either one and the total swings across orders of magnitude — which is exactly why the honest answer is a range, not a figure. And this only counts the observable universe.
So how many stars are in the universe — really?
The number you’ll see almost everywhere is around 200 sextillion — 2 × 1023, or 200 billion trillion. It’s a fine headline, but it hides two important truths. First, it’s not a measurement; it’s a multiplication of two estimates, and reputable sources put the real total anywhere from 1022 to 1024 — a span of a hundredfold. Second, it only counts the observable universe, the bubble of space whose light has had time to reach us. The universe beyond that bubble might be vastly larger, or even infinite, in which case asking how many stars it contains has no finite answer at all. So "200 sextillion" really means "roughly this many, in the part we can see, give or take a factor of a hundred."
How you even estimate such a thing
Nobody counts stars one by one — there is no clicker big enough. Instead astronomers do what you’d do to count the sand on a beach: measure a small patch carefully, then scale up. The "patches" are galaxies. You estimate how many galaxies fill the observable universe — a 2016 Hubble study led by Christopher Conselice put it at around 2 trillion — and you estimate a typical number of stars in a galaxy, often using our own Milky Way as the model at roughly 100 billion. Multiply the two and you land near 2 × 1023. The widget above is exactly that calculation, with both numbers left in your hands.
Why every digit is a guess
Slide either control above and the answer leaps by factors of ten, because both inputs are genuinely uncertain. The galaxy count of 2 trillion was itself a tenfold jump on the previous estimate, and some newer surveys argue it should be back down in the hundreds of billions. The "stars per galaxy" figure is shakier still: most galaxies are tiny dwarfs with a few hundred million stars, while giants like Andromeda hold a trillion, so the average you pick swings the total enormously. On top of that, most stars are too faint to detect individually — one survey caught only about half the stars it expected — and the count is never still, as stars are constantly being born and dying. Put together, that’s why no honest answer is a single number.
More than all the sand on Earth
The classic way to feel the size of this number is to weigh it against sand. Every beach on Earth holds something like 7.5 × 1018 grains — seven and a half quintillion. The observable universe holds around 2 × 1023 stars. That means there are tens of thousands of stars for every single grain of sand on every beach in the world. And our perspective on all of this is humbling: step outside on the darkest night and you’ll see only about 5,000 stars, every one of them in our own galaxy — while the Sun you orbit is just a single, ordinary grain in that cosmic beach.
Where the counting has to stop
Every figure on this page comes with a hidden boundary: the observable universe. Because light travels at a finite speed and the universe is only about 13.8 billion years old, we can only see objects whose light has had time to arrive — a sphere stretching about 46.5 billion light-years in every direction (the space has expanded while the light was in transit). Beyond that edge, there is almost certainly far more universe; many cosmologists think it may be infinite. If it is, then "how many stars are in the universe" simply has no number for an answer. Stranger still, the edge is moving: as cosmic expansion accelerates, distant galaxies are being stretched out of view, so the observable universe of the far future will hold fewer galaxies to count, not more.
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A confident kind of not-knowing
It would be easy to read this page as a failure — we can’t count the stars, we don’t know the real number, we can’t even see most of the universe. But look again at what we can do. From a small planet, in a single average galaxy, using a handful of sampled patches of sky, we’ve pinned the count to within a factor of a hundred and shown our work. We have, in effect, measured the size of our own ignorance.
That’s the difference between a guess and an estimate. A guess is a number with nothing behind it. An estimate is a range with a method behind it — a statement of how much, how sure, and where the knowing runs out. "200 sextillion, give or take, in the part we can see" is not a shrug. It’s one of the most carefully reasoned sentences our species has ever written.
So how many stars are in the universe? Around 200 sextillion that we can see — and an honest, wide-open question mark beyond.
Sources
- European Space Agency (ESA), How many stars are there in the Universe? — the 10²²–10²⁴ estimate and the galaxy-sampling method.
- Space.com & the journal Nature — Christopher Conselice’s 2016 Hubble study estimating ~2 trillion galaxies.
- Wikipedia, Observable universe — the ~10²⁴ upper figure, the 46.5-billion-light-year radius, and the infinite-universe caveat.
- Commonly cited sand-grain estimate (~7.5 × 10¹⁸) and Milky Way star count (100–400 billion) from NASA / ESA Gaia figures.