Towing Capacity Calculator

A vehicle’s headline towing capacity is only one of several limits. The trailer’s tongue weight uses up payload, passengers and cargo count against the combined weight rating, and the hitch has its own rating. Enter your numbers from the door-jamb sticker and owner’s manual, and this calculator checks them all at once and tells you which limit you hit first.

The ratings that matter

The real limit is whichever of these you reach first — and it’s often payload or GCWR, not the headline tow rating.

How the calculator checks your rig

1. Trailer weight ÷ tow rating shows how close you are; many towers aim to stay at or below about 80% for a margin of comfort.
2. Combined weight = curb weight + passengers and cargo + loaded trailer; it must not exceed GCWR.
3. Tongue weight = trailer weight × tongue percentage; it counts as payload.
4. Payload left = payload capacity − passengers and cargo − tongue weight; it must stay above zero.
5. Hitch class is chosen from typical receiver ratings for the trailer and tongue weight.

Worked example

A pickup rated to tow 7,500 lb with a 12,500 lb GCWR, 4,800 lb curb weight and 1,600 lb payload carries 650 lb of people and gear and tows a 5,800 lb loaded travel trailer at 12% tongue weight. The trailer is 77% of the tow rating. Combined weight is 4,800 + 650 + 5,800 = 11,250 lb, 1,250 lb under GCWR. Tongue weight is 696 lb, leaving 1,600 − 650 − 696 = 254 lb of payload. It works — but adding two more passengers and a loaded cooler could use up the remaining payload.

Typical receiver hitch classes

Ratings vary by manufacturer; always use the lowest rating in the chain — receiver, ball mount, ball, coupler and safety chains.

Tongue weight and stability

Too little tongue weight (under about 10% on a ball-hitch trailer) can make a trailer sway dangerously; too much overloads the rear axle and lightens the front, affecting steering and braking. Load heavy items over or slightly ahead of the trailer axles, and measure tongue weight with a tongue scale or a bathroom scale method for light trailers. Weight-distribution hitches spread tongue weight across the tow vehicle’s axles but don’t increase payload or tow ratings.

Before every trip

• Check tyre pressures on vehicle and trailer, including the spare.
• Confirm coupler latch, pin, safety chains crossed under the tongue, and breakaway cable.
• Test trailer lights and brakes; set brake controller gain.
• Adjust mirrors — extended towing mirrors if the trailer is wider than the vehicle.
• Do a walk-around after the first few miles and at every stop.
• Leave extra following distance and slow down on descents.

Trailer brakes and speed

Many jurisdictions require brakes on trailers above a certain weight, often somewhere between about 1,500 and 3,000 lb (750 kg in many European countries), and speed limits for towing are frequently lower than for cars. Check the rules where you tow. An electric brake controller in the tow vehicle lets you adjust how strongly the trailer brakes, which should be set with the loaded trailer on a dry, empty road.

Weigh your rig

Brochure weights are estimates. A trailer’s “dry weight” excludes water, propane, batteries and gear, which can add hundreds of pounds. Public truck scales at travel centres weigh each axle for a small fee; weighing the vehicle alone and then with the trailer gives real numbers for every check above.

Towing planner pack

The optional pack includes a printable pre-tow checklist, a weigh-station worksheet that calculates tongue weight and payload from axle weights, a trailer loading log and a maintenance record. The calculator above is free.

AI-assisted content

This page was drafted with AI assistance and reviewed by Kedop. Always follow your vehicle and hitch manufacturers’ ratings and local towing laws.