How To Calculate 5th Wheel Towing Capacity

Let me try to break it down in simple steps how to calculate your truck’s towing capacity with a 5th wheel!

I had an incredibly hard time with this.  In my mind I didn’t understand why I couldn’t just look up a specific number for what our truck could tow and compare it to the weight of the trailer and get my answer.  But, it’s not quite that easy.  However, I’m an ‘explain it to me like I’m 5 years old person’ so I’m going to try to help you easily calculate your weights.

Let me preface by saying what this post is not about.  This is not a debate about what you were able to pull with your Special Snowflake Truck that has had all sorts of after-market changes.  Nor, what crazy load you were able to pull while ignore all manufacture recommendations and public safety.  This post is for people who have a current truck or considering buying one and want to know they are within basic manufacture and safety specs of a truck’s carrying capacity.

Legal Jargon:

This post is not intended to be a legal post nor an “end all” of towing.  There are after market breaks, tires, etc. that can effect your trucks towing specs.  This is only a informational page on how I’ve found to easily calculate weights. You are still responsible for knowing and operating within the safety specs of your particular truck.  

Now on to the good part.  Here is a break down of what you’ll need to get started.  And I promise…. you will need all of these.


  • GVWR (Gross Vehicle Weight Rating) Generally found on inside door sticker, manual, or on manufactures published Towing Guideline.
  • GCWR (Gross Combination Weight Rating) Generally found on inside door sticker, manual, or on manufactures published Towing Guideline.
  • Curb weight of truck (Empty Factory Weight) Often times found in manual or on manufactures published Towing Guideline.
  • Passenger & Cargo Weight of truck (What do you, your family, pets, anything loaded inside or in the bed weigh?
    •  Also calculate your fuel tank gallons x 6.3lbs for your weight of fuel.  Add this all together.


  •  GVWR (Gross Vehicle Weight Rating) Generally found on a sticker in the trailer near the door.
  • UVW (Empty Vehicle Weight Rating)  Generally found on a sticker in the trailer near the door.
  • Water & Fuel Weight  Generally found on a sticker in the trailer near the door.


Step 1 Calculate Pin Weight.  This is the weight of the trailer that sits on the trucks axles when you connect trailer to truck.

Pin Weights can vary wildly based on if you overload the front part of the trailer or you leave it rather empty.  For this post we are going to assume you’ve loaded with balanced weight throughout the trailer and overall you haven’t exceeded the GVWR of the trailer.

  • Take 20% of the Gross Vehicle Weight Rating of the trailer = Pin Weight

The super OCD way is the second option below.  And honestly, not necessary as long as you don’t exceed the GVWR of the trailer.

  • Take the empty weight of the trailer + your cargo (your personal stuff) + water weight, + Fuel Weight. and then take 20% of that number = Pin Weight


Step 2 – Calculate your Payload. This is what your truck can actually carry.

  • Take the GVWR of the truck minus (-) the Curb weight (empty truck) = Your Truck’s Payload.


Step 3

  • Now add together your people + pets + truck fuel + cargo of the truck + Loaded pin weight I mentioned above and total it.

Does all that add up to less or more than your Payload?  If it exceeds it then you’ve overloaded the truck and you do not pass “Go”.


Step 4

Calculating Gross Combination Weight.  This is where the magic happens!

  • Take your Truck Curb Weight + People + Pets + Truck Fuel+ Truck Cargo + GVWR of Trailer OR the second method above = “Magic Number”

Now compare the “Magic Number” to your Gross Combined Vehicle Weight Rating (GCWR). Are you right on, over, or under?

Ideally you should be about 20% under the GCWR number.

This means you have the pulling and stopping power to control truck and trailer even thru high grades. If you’re right on the number then you may risk overheating while pulling up steep grades or the trailer may push you down hills. If your “Magic Number” is over the GCWR in addition to being over specs and risk damaging your truck, you’re also at legal & liability risk if you’re in an accident.

You may also like...

2 Responses

  1. Good post, you explained it very well. Learning the terms is the first part, after that it’s calculation 🙂 Most people don’t understand the GVWR & the GCWR.

Say something awesome

%d bloggers like this: