# Tow Capacity Math

By Michael Vatalaro

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

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

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. Jot the numbers down so you can add them up.

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, and everything else in or on the truck can weigh before the truck is overloaded. For trailering purposes, tongue weight (the downward weight on the hitch) counts against payload. You're not likely to see GVWR listed on a website, but curb weight and payload are easy to find.

Curb Weight + Towing Capacity + 180 lbs. = GCWR

Gross Combined Weight Rating (GCWR) is the maximum weight the truck can safely get moving — and stop! Frequently equal to the vehicle's curb weight plus the towing capacity and the assumed weight of the driver, you'll sometimes see GCWR listed, but more often it's easier to find towing capacity and do the math.

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 in the equation for any passengers or gear in the truck. Experts suggest that the weight of the fully loaded boat/trailer be no more than 85 percent of the tow capacity to allow a reasonable payload in the truck.

What does your boat and trailer weigh? If you're unsure, a trip to the truck scales might be in order. See "Tongue Weight DIY" for a refresher on measuring the total weight and tongue weight of your rig.

Michael Vatalaro is BoatUS Magazine's executive editor.

— Published: Spring 2015