Determining Towing Capacity

The basic concept of calculating towing capacity isn’t exactly complicated: your vehicle needs to be capable of towing whatever it is you’re trying to tow, and you should never go over that limit because it’s dangerous (and potentially deadly). But actually calculating towing capacity and understanding the details to be sure you’re within safety limits gets a bit complex.

It’s important to remember you can never have too much truck, when it comes to towing.

Doing the calculations for towing capacity involves math, but it’s straightforward: some addition and subtraction and comparing two numbers. The tricky part is finding the data you need because there’s no single source for all things weight-related, and the only way to be sure you’re under capacity is by visiting a weigh station to have your vehicle and RV weighed separately.

Here are the important terms and definitions:

Vehicle curb weight, or dry weight: The weight of your vehicle (the one doing the towing) completely empty. This can be found on a sticker inside the door frame, in the owner’s manual, or elsewhere from the manufacturer, but it’s often an impractical measurement: it’s the weight with no driver, no passengers, no cargo, no extra features, maybe even an empty gas tank. The only way to get an accurate actual curb weight for your specific vehicle is to take it to a weigh station and weigh it with no one and nothing in it.

GVWR, or Gross Vehicle Weight Rating: The maximum amount your vehicle can safely weigh, including all passengers, cargo, and the weight of the trailer hitch (see below). This is provided by the manufacturer on a door sticker, owner’s manual, or other manufacturer’s publication.

GCVWR, or Gross Combined Vehicle Weight Rating: The maximum weight of the combination of vehicle and trailer, including all passengers, cargo, water and waste tanks, propane, food, and toys. This is provided by the vehicle’s manufacturer.

GCVW, or Gross Combined Vehicle Weight: The actual weight of the vehicle plus trailer, including all passengers, cargo, water and waste tanks, propane, food, and toys. The only way to get an accurate GCVW is by taking your vehicle and trailer to a weigh station like a CAT Scale or Escapees SmartWeigh.

Trailer Dry Weight: The weight of of a completely empty trailer. Manufacturers’ definitions of “empty” can vary widely, and may or may not include propane, water, waste, or extra features. This number can be found on a sticker from the manufacturer, but the only way to get an accurate dry weight is to take your trailer to a weigh station and weigh it empty.

Trailer GVWR, or Gross Vehicle Weight Rating: The maximum amount your trailer can weigh, including all cargo, full water and waste tanks, and propane. This is provided by the manufacturer on a sticker or other manufacturer publication.

The manufacturer's sticker describing the trailer's weight ratings.

Hitch weight, or tongue weight: This is the amount of weight exerted vertically (downward) on the hitch ball. Hitch weight is generally about 10% of the trailer’s GVWR, but is provided by the manufacturer and can be measured by yourself with a trailer tongue weight scale. Remember that tongue weight can vary, depending on the amount of gear loaded towards the front of the trailer and loaded on the tongue itself.

Payload rating: The maximum weight that can be hauled inside the vehicle doing the towing, including driver, passengers, cargo, and the hitch weight. A payload rating is published by the manufacturer, but can also be calculated by subtracting the the vehicle’s curb weight from the GVWR.

Payload: This is the actual payload, or the total weight of the driver, all passengers (including pets!), cargo, and the hitch weight. This can only be accurately determined by taking the loaded vehicle to a weigh station and subtracting the vehicle’s curb weight.

Can I Tow This? If GCVW is less than GCVWR, then you are within the towing capacity of your vehicle, so yes, you can (probably) tow this.

The Math

  • GCVW = Truck Curb Weight + Driver + Passengers + Truck Cargo + Trailer Dry Weight + Trailer Cargo
  • Payload Rating = Truck GVWR – Truck Curb Weight
  • Payload = Driver + Passengers + Truck Cargo + Hitch
  • Trailer GVWR = Trailer Dry Weight + Trailer Cargo
  • Goal: GCVW < GCVWR

The Calculator

Because I was constantly having trouble remembering all the differences between the somewhat similar acronyms, I created a towing capacity calculator with all of the above math and definitions, and used it while we were shopping for our RV and truck:

Can I Tow This?

The Research

Trailer Life Tow Guides are an outstanding resource, because they are annual publications offer the tow ratings for most vehicles going back to 1999, and free to use. We used these while shopping for our truck, because we purchased the trailer first, and needed to make sure whatever we bought could tow our RV.

This calculator (and this post) do not factor in more subtle concerns about towing capacity, such as Gross Axle Weight Rating (GAWR), which more specifically defines the amount of weight that each axle can carry. In most cases, GAWR is factored into a trailer’s GVWR, but if you’re hauling very uneven loads (where one end of your rig is disproportionately heavier than the other end), you may need to dig a little deeper into the numbers and weights. If you’d like to know more, How Stuff Works has an interesting article about GAWR and why it’s important.

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