As stated above go to a local scale (www.catscsle.com
). Truck scales are easiest but you can also use a local dump station scale. You want a total truck weight but getting individual axle weights is helpful. If at a truck scale weigh front axle on scale pad one and rear axle on scale pad two. The ticket will give you a total weight as well. Most cat scales at $9-12 for first weigh and $1-2 for reweigh in a 24 hrs period. You want to weigh with full tank of fuel and all passengers, pets and gear you intend to have on board when towing.
Take your total truck weight and subtract it from gcwr to get your adjusted tow capacity. Take your total truck weight and subtract it from gvwr to get your available payload. Take your scaled rear axle weight and subtract it from grawr to see how much weight you can put on your rear axle for pin weight if looking at a fiver.
Your loaded (not dry) weights need to be less than available tow capacity and loaded tongue weight needs to be less than available pin weight. Ideally loaded tongue weight is 13-15% of loaded tt weight. Loaded pin weight of a fiver is typically 20-23% of loaded fiver weight. If you dont know how much you will add to a trailer know that typically people add 1000-1500 lbs of cargo to a trailer but safest is to calculate using trailer gvwr.