limit could allow you to go as large as a 16' trailer, though some will approach the limit. If that is the tow rating of your vehicle, you have to consider extra people, pets, and gear in the vehicle. Tow ratings generally assume two people in the front and the rest of the vehicle empty.
The thread Trailer Weights in the Real World
is a helpful place to start. It has actual loaded weights of different makes and models, new and vintage. Post #297 links to a spreadsheet of the data.
We travel with 4 people and our 13' Scamp
is tight, but cozy. The upper bunk is weight-limited, but the actual limit is not published.
I've heard different numbers, but 100-120 pounds seems reasonable. Our girls have gotten to the age where they'd rather have their own tent when conditions allow, but it's nice to know we can all fit inside when the storms howl and the bears prowl! We bring lots of toys and gear, so our Pilot (rated 3500/350#) gives us some wiggle room on weight