What is Tongue Weight and How Do You Measure It?

A Brief Guide on Tongue Weight and How to Measure It

Measuring tongue weight
••• Measuring tongue weight is essential to preventing trailer sway when towing. Clinton Freeman/EyeEm/Getty Images

Tongue weight is one of the integral parts of towing any trailer. Whether you’re a beginner or an experienced RVer, knowing what tongue weight is, how to calculate it, and how to adjust it are essential to staying safe while towing.

What is Tongue Weight?

Tongue weight is the downforced force from the tongue of the trailer to the hitch of your towing vehicle. The industry standard for tongue weight is anywhere between nine percent and 14 percent of your gross trailer weight (GTW.) Tongue weight allows you to control the trailer when hitched, which makes driving safer.

When tongue weight is improperly calculated, it contributes to trailer sway and cause accidents when towing.

Technical Aspects of Tongue Weight

For the more experienced RVer, tongue weight is a lever. The trailer’s axle is the fulcrum, and that’s where the lever pivots when being towed. This allows for a trailer to turn and adjust to road conditions, speed, and the wind without snapping back and forth all over the place. When your tongue weight is level, you’ll avoid most sway. If tongue weight is light, the weight shifts behind your axle; if tongue weight is heavy, it shifts ahead of your axle. This affects how your RV or trailer sways, stops and moves on the road.

Visualizing Tongue Weight

The easiest way to determine if tongue weight is an issue is to take a step back from your setup after setting up up your hitch. Look at the trailer itself and the towing vehicle. If either is leaning forward or backward, then your tongue weight is uneven, and you’ll have issues when towing.

Determining Tongue Weight

There are a handful of ways to figure out the proper tongue weight for your RV setup. Depending on whom you talk to, they’ll swear by one method and shoot down another. It’s important to find the right way to determine tongue weight for you. It takes some practice to get the weigh-in right, but it’s important that you take the time to learn how to calculate and adjust it.

Pro Tip: Remember that the tongue weight should be between nine percent and 14 percent of the GTW, depending on the setup. Check with the manufacturer guidelines of your RV and towing vehicle for the proper weight.

The equation for calculating tongue weight is simple:

GTW X Percent (Manufacturer recommended) = Tongue Weight

Measuring and Adjusting Tongue Weight

As we said before, there are different ways to adjust tongue weight. Once you’re experienced, you’ll be able to do it by eye in most situations. For now, you’ll want to find a method most comfortable to your setup.

Tongue Weight Scale to Measure Tongue Weight

If you are traveling and checking your tongue weight each time, you can make it easier on yourself by purchasing a tongue weight scale. Tongue weight scales are compact specialized devices that take the guesswork out of measuring. This is by far the best way to measure tongue weight if you can’t make it to a commercial weigh station.

Here's how to measure tongue weight with a tongue weight scale:

  • Park your vehicle and trailer on a hard level surface.
  • Slide the scale underneath where your trailer tongue jack touches the ground.
  • Crank down the trailer jack until it is pressed onto the scale.
  • Detach the trailer from the hitch and take your reading.

Most tongue weight scales can handle up to 2,000 pounds or roughly a 20,000-pound trailer. Make sure you read the capacity of the scale before purchasing and follow any instructions for how to use the scale related to your towing setup.

Bathroom Scale to Calculate Tongue Weight

If your gross trailer weight is smaller, such as 3,000 pounds or lighter, you may be able to use a bathroom scale to measure your tongue weight. This method is a bit more complex than a tongue weight scale but is easy once you get the hang of it.

Pro Tip: Using a bathroom scale to calculate tongue weight can be done, but it may not be as accurate as using a tongue weight scale or visiting a commercial weight station. Keep that in mind if you’re coming close to your weight limit.

Make sure your bathroom scale is up to the challenge of supporting the weight or else you’ll have a broken scale and no reading. We recommend investing in a bathroom scale to measure tongue weight versus using the one from your bathroom.

You will need a bathroom scale, one brick, two pieces of pipes, and a 2’ x 4’ piece of lumber four to five feet long.

Here are the steps to follow to use a bathroom scale to measure tongue weight:

  • Lay the brick and scale three feet apart from each other and make sure they are the same height.
  • Lay a pipe across long ways across both the brick and the scale.
  • Set your 2’ x 4’ on top of the pipes.
  • Place the ball socket of your tongue on top of the 2’ x 4’ two feet from the scale and one foot from the brick.
  • This will distribute the weight at a 3:1 ratio on the scale.
  • Make sure the socket is at the same height as your ball hitch. (You may need to use an extra piece of wood on top of the 2’ x 4’ for this.) 
  • Now get the reading on your bathroom scale and multiply by three since the weight on the scale is at a 3:1 ratio and you have your tongue weight.

Commercial Weight Scale to Find Tongue Weight

This one involves a few steps, but it is simpler than using a bathroom scale. Drive your trailer to a commercial scale at a truck stop or material supply center. 

Here's what to do at a commercial weight station to measure your tongue weight:

  • Drive only your vehicle onto the scale with the loaded trailer attached; make sure all four of your tires are on the scale.
  • Take the weight measurement, and this is measurement X. 
  • Detach the trailer from your vehicle while your vehicle remains on the scale.
  • Take the measurement, and this is measurement Y. 
  • Now subtract Y from X, this is your approximate tongue weight.

Play around with these different methods to find out which one suits you the best. It takes some practice with each method to get it down right. Once you find the most efficient way to measure tongue weight for your towing setup, towing your trailer will be safer for you. Before you know it, you’ll be a tongue weight measuring machine!

Trailer sway is a deadly hazard on the road. When your trailer is out of control, it will collide with other vehicles or pull you off the road. In severe weather, this can be tragic.  Understanding tongue weight is essential to staying safe when towing a vehicle, no matter where you’re going or what you’re towing.

Read More

  • Want to prevent trailer sway? Should you double up on safety chains to do it? Read this guide on safety chains.
  • Learn more about towing weight, towing acronyms, and more with this guide on towing capacity.
  • Need to understand curb weight, dry weight, and more? Read this guide on curb weight.