I followed other reviewers in sizing up. I have two small Labs - 55 and 63 lbs which would both fall under the Large. I sized up, going with the XLarge. It's HUGE!!! They can both lay in it if they are curled and it's much bigger than either of them even when stretched out.
I'm not saying you should not size up - I'm actually very pleased with the size, but I think we would have been fine with the large.
I do very much love this bed - along with the our other Westpaw products (crate pads and a square bed). It's durable and easy clean and both of the Labs love it.