The observable universe is about 93 billion light-years across, forming a sphere around us with a radius of roughly 46.5 billion light-years in every direction.

How Big Is the Observable Universe? (Quick Scoop)

The headline numbers

  • Radius: About 46.5 billion light-years from Earth in any direction.
  • Diameter: About 93 billion light-years across.
  • Volume: Roughly 3.6×10803.6\times 10^{80}3.6×1080 cubic meters (an almost unimaginable amount of space).
  • Ordinary matter inside: About 1.5×10531.5\times 10^{53}1.5×1053 kilograms (stars, gas, dust, planets, you, everything).

A light-year is the distance light travels in one year, so when we say “billion light-years,” we’re talking about distances so vast that even light needs billions of years to cross them.

Wait, if the universe is 13.8 billion years old…

You might think the farthest we can see should be 13.8 billion light-years , since the universe is about 13.8 billion years old. But there’s a twist:

  1. The light we see today from the most distant regions has indeed been traveling for about 13.8 billion years.
  1. However, space itself has been expanding the whole time (this is what Hubble’s law describes).
  1. So the galaxies that emitted that ancient light are now much farther away than 13.8 billion light-years—about 46 billion light-years away today.

In other words, the observable universe isn’t limited just by “how long the light has been traveling,” but also by how much space has stretched during that journey.

What “observable” really means

“Observable universe” does not mean “the whole universe.” It means:

  • The bubble of space from which light (or other signals) has had time to reach us since the Big Bang.
  • Anything beyond that bubble is currently causally disconnected from us: no light, no information, nothing from there has reached Earth yet.

So when we ask “how big is the observable universe,” we are really asking:

How far out can we, in principle, receive information, given the universe’s age and its expansion?

Current estimates suggest the entire universe may be much larger than the observable part—possibly vastly larger, maybe even effectively infinite—but we cannot see or measure it directly.

A quick mental picture

Imagine:

  • You’re inside a growing loaf of raisin bread.
  • The raisins are galaxies.
  • As the dough (space) expands, every raisin sees the others moving away.
  • Your observable universe is the spherical region of bread from which light from those raisins has had time to reach you since the loaf started rising.

The key: the loaf has grown while the light was traveling, so the raisins you see as they were billions of years ago are now much farther away than “time × speed of light” would suggest.

Latest context and ongoing work

  • The ~93 billion light-year diameter comes from precise measurements of the cosmic microwave background, galaxy surveys, and the standard cosmological model (ΛCDM).
  • New telescopes and missions (like JWST and upcoming observatories) keep refining details—such as how fast the universe is expanding—but they still point to a similarly sized observable bubble on these scales.
  • Popular science videos and recent explainers now focus a lot on the difference between “age” and “size,” because that’s the part that most people find counterintuitive and is a frequent topic in forum discussions and Q&A threads.

TL;DR

  • The observable universe is a sphere about 93 billion light-years across , centered on us.
  • We see only this bubble because light hasn’t had time to reach us from beyond it.
  • The actual universe is very likely far larger—possibly unimaginably so—but currently beyond our observational reach.

Information gathered from public forums or data available on the internet and portrayed here.