For the max tongue weight possible for your unit, take gvw and multiply by .15 (15%). That figure will be the max tongue weight you should ever have. I myself would go 1 bar size over that so you have a little "cushion" if you decide to move up to a larger trailer in the future.
As others have stated, "The CAT scale is your friend".
You should scale your unit so that you know what you weights are and know that your hitch is adjusted correctly.
'07 Chevrolet Silverado 3500HD XC LB SRW 4X2.
Powerstop Brakes on all corners.
'15 JayFlight 28BHBE Elite Fibreglass
'07 Northern Lite 10-2RR Camper.