How big is the universe?

At least 420 trillion cubic light years

Determining the size of the universe is very tricky due to the fact that the main method we have for exploring the universe is light. As light has a finite speed limit, it takes some time to get from one place to another. While this speed is incredibly fast, the universe is also incredibly large; light from some of the most distant galaxies takes an incredible 13.8 billion years to reach us. Given the speed limit of light, there are parts of the universe that are so far away that light has not had long enough to reach us over the entire history of the universe. The volume within this distance is called the ‘observable universe’, which has a radius of 46.5 billion light years.

The size of the universe outside this is unknown, as we cannot see it, but estimates suggest it’s 250 times the size of the observable universe at a staggering 420,000,000,000,000 cubic light years!