Applying Bayesian model averaging to various cosmological models of the universe, astrophysicists at the University of Oxford and Imperial College London have found that the most likely model is that the Universe is flat.

A flat Universe would also be infinite and their calculations are consistent with this too. These show that the Universe is at least 250 times bigger than the Hubble volume (similar to the size of the observable universe).

Ref: arxiv.org/abs/1101.5476: Applications Of Bayesian Model Averaging To The Curvature And Size Of The Universe