You can measure it with a tongue weight scale or a bathroom scale and a lever, or at a CAT scale by weighing the vehicle with and without the trailer attached.
How the towing calculator works
TowCapacityCalc multiplies the loaded trailer weight by the tongue percentage to get the tongue (or fifth-wheel pin) weight, then compares it with the usual range for the trailer type: 10–15% for a conventional bumper-pull trailer, 15–25% for a fifth wheel and 20–25% for a gooseneck. It divides the trailer weight by your towing capacity and flags anything above the 80% rule of thumb, subtracts people, cargo and tongue weight from payload, and suggests the lowest receiver hitch class rated for both the trailer and the tongue weight. Weights work in pounds or kilograms.
Receiver hitch class chart
| Class | Max trailer | Max tongue | Typical use |
|---|---|---|---|
| Class I | 2,000 lb | 200 lb | cars and small crossovers, bike racks, small utility trailers |
| Class II | 3,500 lb | 350 lb | crossovers and minivans, small boats and campers |
| Class III | 8,000 lb | 800 lb | pickups and SUVs, most travel trailers and boats |
| Class IV | 10,000 lb | 1,000 lb | full-size pickups and SUVs, larger campers |
| Class V | 20,000 lb | 2,000 lb | heavy-duty pickups, equipment and car haulers |
Ratings are typical maxima; your hitch’s label and the vehicle’s manual are the final word. The towing capacity, payload, GVWR, GCWR and axle ratings all apply at once, and the lowest one is your real limit. Weigh the loaded rig at a truck scale before a long trip.
Frequently asked questions
What percentage should tongue weight be?
10–15% of the loaded trailer weight for a conventional trailer; many experts aim for about 12%.
What happens if tongue weight is too light?
Below about 10% the trailer is more prone to sway. Move heavy cargo forward of the trailer axles.
How do I reduce tongue weight?
Move cargo back toward or behind the axles, empty front water or propane tanks, or move a toolbox off the tongue.
Is TowCapacityCalc free?
Yes, with no sign-up or ads, and your numbers stay in your browser.
Is this a substitute for my vehicle ratings?
No. It is an estimate. Always follow the owner’s manual, the door-jamb sticker and the hitch and trailer ratings, and weigh your rig at a scale.