In motor vehicles, the gross trailer weight rating (GTWR) is the total mass of a road trailer that is loaded to capacity, including the weight of the trailer itself, plus fluids, and cargo, that a vehicle is rated to tow by the manufacturer. In the United States and Canada, the static tongue load, the weight of the trailer as measured at the trailer coupling, is generally recommended to be 10-15% of the GTWR.
In the United States and Canada, there are four main weight classes of trailer hitches as defined by the Society of Automotive Engineers (SAE):
References
Gross trailer weight rating Wikipedia(Text) CC BY-SA