There's no easy answer to this question.
If referring to the observable universe, that being defined as everything we can in principle observe from Earth, its radius is about 46 billion light years. That's approximately 276 sextillion (276,000,000,000,000,000,000,000) miles!
However, the Universe as a whole is possibly infinite in size. There's simply no way for us to currently calculate where the boundaries, if any, are, and it's possible there never will be.