Hi Tracks -
It's not just the size of the hernia that determines whether you need surgery. There are many factors, including whether the surgeon feels you need it.
There are two types of hiatal hernias. Sliders, the ones that go up and back down again, unless they are huge, generally don't cause symptoms bad enough for surgery. Paraesophageal hernias, the kind where a part of the stomach is stuck in the chest, on the other hand, will never get better on their own and can strangulate, and you generally die from that. So PEH needs the operation. That was t he type I had.
Other important factors include things like whether your swallowing reflex is working properly. There are different operations for that. Mine wasn't working well, but still not a nutcracker case, so I had the partial wrap known as Toupet Fundoplication.
You need lots of tests to prove whether you are a candidate for a wrap. Read all the stuff in the permanent posts at the top of the forum! One I sent in has good descriptions and pictures of the different types of operations.