Your tow vehicle has its own weight limit, and towing eats into it fast. Work out what's actually left once occupants, accessories and tow-ball mass are accounted for.
Work out your vehicle's remaining payload
Estimate only. Fuel, fluids and factory options already sit inside your kerb weight — check your compliance plate and get a weighbridge check before you rely on these numbers. See Vehicle Payload When Towing: What Australians Often Miss.