How Tongue Weight Works

By: Scott C. Benjamin  | 
Car with a trailer hitched up drives alongside a body of water.
Tongue weight is critical to know, yet simple to calculate and easy to adjust.
Jyrki Komulainen/Getty Images

­Eve­r­yone should know his or her tongue weight. Don't laugh to­o hard about the way that sou­nds­ — tongue weight is a towing­ term, not something t­o do with the human mouth or dentistry.

Tongue weight (TW) is just one of the many towing terms you'll need to familiarize yourself with if you ever intend to tow a trailer behind your vehicle. It's the downward force that the tongue of the­ trailer applies to the hitch of the tow vehicle. In this article, we'll help you determine tongue weight for your towing needs and ensure you're ready to explore the great outdoors safely!


What's the Proper Tongue Weight?

Most experts agree that an acceptable tongue weight for any trailer is somewhere between 9 and 15 percent of the gross trailer weight (GTW). There's good reasoning behind these numbers, too. It all comes down to trailer towing safety.

If the tongue of the trailer does not exert enough downward force on the tow vehicle's hitch ball — meaning that the trailer's tongue weight is too light — a dangerous condition called trailer sway could result. If the tongue weight is too heavy, the steering of the tow vehicle will be affected. This makes it sound like tongue weight is a big deal, and it is. But fortunately, tongue weight is also easy to adjust.


Too Little or Too Much Tongue Weight?

Just remember that the trailer acts like a lever, and the axle of the trailer is the fulcrum (or pivot point) for the lever. If the tongue is too light, you need to move some of the cargo forward of the trailer's axle. If the tongue is too heavy, you need to adjust the load so that more of the weight is behind the trailer's axle. It's just like trying to balance the weight of two kids on a seesaw at the playground.

That's easy enough to understand, but other than simply lifting the tongue of the trailer and guessing its weight, how could you ever know how much the trailer's tongue truly weighs? And an even better question may be this: How would you determine if the tongue weight falls within the 9- to 15-percent range of the gross trailer weight? Read the next page to find out how you can do just that.


Calculating Tongue Weight

A profile view of a car hitched to a trailer, showing the uneven tongue weight.
The front wheels of the tow vehicle are barely on the ground. Is the tongue weight too heavy?
Blaine Franger/Getty Images

Finding the tongue weight of any trailer can, at first, seem like a difficult task. Fine-tuning the tongue weight to fall within the 9- to 15-percent weight range of the gross trailer weight (GTW) might seem nearly impossible. You'll be happy to know that it doesn't have to be complicated at all.

Most trailer owners already know their gross trailer weight, which is the actual weight of the trailer. If you don't know your gross trailer weight, then you'll need to plan a trip to the local public scales. With an investment of only a few dollars and just a little bit of your time, you can get some valuable information. Knowing your gross trailer weight is critical to properly adjusting the tongue weight of your trailer. In fact, it's your starting point in a very simple equation.


As an example, let's say that your gross trailer weight is 564 pounds (256 kilograms). If you're trying to adjust your tongue weight to 11 percent of the gross trailer weight, then you want the tongue to weigh 62 (28 kilograms) pounds. Easy enough, but how do you find out how much the tongue weighs right now?

Use a Tongue Weight Scale

Since this is a smaller trailer, you can measure tongue weight by using a standard bathroom scale. The trick is to make sure that the scale is at the same height as the hitch ball on the tow vehicle. Usually a small box or a cinder block will do the trick. Next, carefully place the tongue of the trailer directly on the scale and read the weight. This is your tongue weight.

If the tongue weight is more than 62 pounds (28 kilograms), then you need to move some of the trailer's cargo rearward so that more weight is carried behind the trailer's axle. If the tongue weight is less than 62 pounds (28 kilograms), then you'll need to adjust some of the cargo toward the front of the trailer so more weight is carried in front of the trailer's axle. Keep your eye on the scale and you should be able to hit the target tongue weight.


Ascertaining Larger Trailer Tongue Weight

For much heavier trailers — those with a tongue weight that would exceed the weight limit of a standard bathroom scale — you need to employ a slightly different technique. There are two very good options available to you. First, you could purchase a tongue weight scale that's designed specifically to measure trailer tongue weights (up to one ton). Or, with a little extra effort and some additional setup time on your part, you can use the same standard bathroom scale.

To do this, you'll need a two-by-four cut to a five- or six-foot (1.5- or 1.8-meter) length, two pipes, your bathroom scale, and a brick. Lay one of the pipes across the scale and the other across the brick. Position the scale and the brick so the pipes are exactly three feet apart.


Now, lay the two-by-four across the pipes, and find a suitable way to support the tongue of the trailer at the same height as the tow vehicle's hitch ball. Place the tongue (and hitch-height support) on the two-by-four exactly 2 feet (0.6 meters) away from the pipe lying across the scale and 1 foot (0.3 meters) away from the pipe lying across the brick.

Read the weight displayed on the scale, and then multiply the weight by three. This is your tongue weight. As with the method we used for the smaller trailer, you can adjust the weight of the cargo forward or rearward of the trailer axle to reach your target tongue weight. Just watch the scale, and don't forget to multiply the displayed weight by three.


Learn Your Proper Tongue Weight Range

Measuring tongue weight isn't really that complex. In fact, with enough practice, you'll soon be a pro at finding tongue weight — and the way your trailer handles on the road will reflect that. Plus, your due diligence will help you sidestep some potentially disastrous towing risks.

If you're interested in reading more about vehicle weight, towing and other related topics, follow the links on the next page.


Tongue Weight FAQs

How do you calculate tongue weight?
1. Load your trailer and fill your truck up just as they'll be before your trip and head to a commercial scale. Drive on to the scale so all four wheels of the truck or tow vehicle are on it, but not the trailer. Note the weight. 2. Unhook the trailer and jack up the trailer tongue so there is no weight on the hitch ball. Now record the weight of the truck only. This is your gross vehicle weight. 3. Now subtract the gross vehicle weight from the weight of the truck with the trailer attached to get the tongue weight.
How much tongue weight is too much?
Most experts agree that an acceptable tongue weight for any trailer is somewhere between 9 and 15 percent of the gross trailer weight (GTW).
How can I increase my tongue weight?
Exceeding your vehicle's tongue weight can lead to damaging it; not to mention the potential damage you can inflict on others. To haul more in the same trailer, you can redistribute the contents within your trailer. Add more weight in front of the trailer's axle for improved handling.
What does 500 lb. tongue weight mean?
Usually, the tongue weight is just a representation of how much you are towing. For example, a 500-pound tongue weight would ideally mean you are hauling a 5,000-pound trailer. However, this is just a rough scale.

Lots More Information

Related HowStuffWorks Articles

More Great Links

  • "Automotive Glossary: Tongue Weight." (Sept. 26, 2008)
  • Curt Manufacturing. "Understanding Towing: Tongue Weight." (Sept. 26, 2008)
  • "Tongue Weight (TW)." (Sept. 26, 2008)
  • U-Haul. "Towing glossary: Tongue weight." (Sept. 26, 2008)