There are more stars in the observable universe than grains of sand on all the beaches on Earth.
Astronomers estimate the observable universe holds somewhere around 10 to the power of 22 to 10 to the power of 24 stars. Estimates for grains of sand on Earth's beaches come out at roughly 10 to the power of 18 to 10 to the power of 19.
Why is this true?
Our own galaxy has a few hundred billion stars, and there are hundreds of billions of galaxies. Both numbers are rough, but the gap between them is so large that the comparison holds however you count.
More facts in this category
More about space
Space facts are mostly a lesson in scale. Days longer than years, storms wider than Earth, light that left its star before the pyramids existed — the numbers stop being intuitive very quickly. Every entry here comes from established astronomy and includes a short explanation of what causes the effect, so the fact holds up when someone asks the obvious follow-up question at the dinner table.