Gross Combined Vehicle Weight Rating (GCVWR) is the rating you need to know to calculate your vehicle's towing capacity.
GCVWR is with the following consideration as well:
The trailer/s you plan to tow
The cargo/es it will carry, i.e., the driver's weight and the wiper fluid
In addition, it's also essential to know your vehicle's curb weight. The curb weight refers to the weight of your car when filled with gas and miscellaneous fluids consumed with the duration of travel.
Now, you need to subtract the curb weight from the GCVWR to get your vehicle's towing capacity.