Does the universe have a definite size?

Answer 1

The universe has been continuously growing since the Big Bang, and there is no way to accurately measure it, so no.

Comments:

In fact astronomers have estimated the size of the "Observable Universe".

They say there's probably a lot more that we can't see.

The Universe is about 13.8 billion years old.

That gives the maximum distance we can observe as 13.8 billion light years.

But while the light from the "edge" of the Observable Universe has been travelling to us, the Universe has been expanding.

Astronomers have estimated how far away that edge is NOW.

The usual estimate given for the "real" radius of the Observable Universe is about 46 billion light years.