Depends on what you define as being the "Universe". If you're talking about the Local Universe (Local Bubble, Hubble Domain...whatever you want to call it), then it's about 95 billion light years across. Now you're probably wondering, yeah, but why do they say it's 13.7 billion years since the Big Bang and yet it's so much bigger than 13.7 billion light years??. Well, it's a matter of what you define as a distance. The value of 13.7 billion is the number of years the light has taken to travel from those objects we see close to the time of the Bang, to us now. That is, the light travel time. The actual physical distance to those objects as they are now, is an entirely different matter. Due to the way the expansion occurs, those objects are in fact further away than the light travel time seems to indicate. In fact, the distance the object is at now is greater than the light travel time multiplied by the velocity of light, c....or thereabouts. This link should explain it fully for anyone wanting to know how far away are they.....
FAQ Cosmology
So, if we mean the Universe as a whole, and not just the Local Bubble, what do we have to consider when talking about the size of the Universe??. The main thing we have to consider is the apparent flatness of the topology (or shape), the Universe presents to our observations. Whilst we can only see to the "event" horizon of the Local Bubble i.e. where the velocity of recession approaches and exceeds the speed of light (c), spacetime itself is much, much larger. Think of it like standing on the Earth and looking out to the horizon. You can only see 10 miles standing at sea level because of the curvature of the planet. That 10 miles is your horizon distance. Now, there's a lot more Earth beyond that we can't see and it's the same with the Universe. Just how big it is we don't really know, only that it's vastly bigger. Because the Universe we see is exceptionally flat, the Universe would have to be at least 20 times as voluminous than the size of what we see. It's at least 70 billion light years in radius, and many figures quoted by the guys in the know (e.g Andre Linde), range from 160 billion upto many trillions of light years in radius.
My own opinion??.....it's most likely many, many trillions of light years across, given how flat the topology is and how finely balanced the critical density of the Universe seems to be with the other factors which govern it.