How to know (or estimate) the range of a transceiver?
You need to develop a Link Budget for your application. You know how much power the transmitter puts out, and you know how much power the receiver requires. You need to account for all of the losses and gains in between those two points.

Most of the items are readily quantified, except for the free-space path loss, which is highly dependent on the distance, the frequency band and the operating environment (rural/urban, indoor/outdoor, multipath, etc.). There are many different ways to estimate path losses, but they all are very rough approximations. In the end, you have to build it and try it.