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Tow Capacity Math

Can your truck tow the boat you want? It's easy to figure out.

Towing a bass boat

Don't forget, pets, coolers, and people all count toward payload capacity. (Photo: Bruce W. Smith)

Whether you recently bought a trailerable boat, or you’re thinking about buying one, you're likely going to need a vehicle that can pull it safely. If you're in the market for a new truck or SUV to tow your boat, we're here to help.

To determine if your vehicle can tow your next boat, you'll need to answer three questions: What does the truck weigh? How much does the boat and trailer weigh? And how much weight can the truck safely accelerate, control, and brake? Assuming you've estimated how much the boat and trailer weigh, you can find the answers to the other questions on the automaker's website, or at such sites as Edmunds.com or Kelley Blue Book but first it helps to know what numbers to jot down, how to add them up, and what acronyms result from the math.

Curb Weight + Payload = GVWR

The Gross Vehicle Weight Rating (GVWR) of the truck equals the truck's curb weight (the total weight of the vehicle with standard equipment) plus its payload capacity. Payload capacity tells you how much the people, gear, pets, and everything else in or on the truck can weigh before the truck is overloaded. For trailering purposes, tongue weight (the downward weight the trailer exerts on the hitch) counts against the payload. Curb weight and payload are easy to find.

Curb Weight + Towing Capacity + 180 lbs. = GCWR

The vehicle's Gross Combined Weight Rating (GCWR) is the maximum weight the truck can safely get moving — and stop! This number is frequently, but not always, equal to the vehicle's curb weight plus the towing capacity (how much your rig can pull) and the assumed weight of the driver (180 pounds), you'll sometimes see GCWR listed, but more often it's easier to find towing capacity and do the math.

Tip

Don’t want to do the math? We've put together a list of the tow capacities for more than 100 2021 SUVs and trucks to help you narrow your search.

These numbers are maximums — neither can be exceeded without compromising safety. When the weight of the boat/trailer combo is added to the curb weight of the vehicle, the total must be less than the GCWR or you risk not being able to control the truck/trailer combo. Similarly, if you max out the towing capacity with a heavily loaded boat and trailer, you'll have no room for any passengers or gear in the truck. Experts suggest that the weight of the fully loaded boat/trailer be no more than 85% of the tow capacity to allow a reasonable payload in the truck.

What's the Tongue Weight?

Tongue weight is the amount of weight a fully loaded trailer exerts on the hitch ball of the tow vehicle. Knowing the tongue weight of your boat trailer is critical for a safe, comfortable towing experience, as well as for improving your tow vehicle's fuel efficiency. Too much tongue weight can cause poor tow vehicle performance. Too little weight, and you risk the trailer swaying, losing control, or the trailer separating from the vehicle.

Your trailer tongue weight should generally be between 10% and 15% of gross trailer weight. For example, a 1,000-pound trailer with boat and cargo should have a tongue weight of between 100 and 150 pounds. You may be able to adjust the tongue weight by redistributing the load or by removing or adding weight.

Most commercial truck scales will weigh trailered boats for a small fee. To calculate your tongue weight, pull the truck onto the scale, leaving the trailer hooked up to it, but keeping the trailer wheels off the scale. Get the weight (let's say it's 4,600 pounds), then drive off the scale, disconnect the trailer, drive the truck back on the scale again, and weigh the truck by itself. Let's say it weighs 4,200 pounds. The difference between the first and second weights (4,600 minus 4,200 = 400) is the tongue weight.

Don't have a truck scale nearby? Here's a method you can use at home using a standard bathroom scale.

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Author

Michael Vatalaro

Contributor, BoatUS Magazine

Michael Vatalaro is the former executive editor of BoatUS Magazine. He has a Pursuit center console, which he uses in the Chesapeake Bay.