Calculating Your Truck’s Maximum Payload and Towing Capacity

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Calculating Your Truck's Maximum Payload and Towing Capacity

November 19, 2019

Whether towing or hauling cargo, you need to know the capacity your vehicle can handle. Exceeding this value can cause excessive wear on your truck’s engine, transmission, tires, brakes and other components. Discover more about towing capacity, payload and other calculations you will need to make to get the most from your truck.

What’s the Difference Between Payload and Towing Capacity?

You see several numbers thrown at you in truck advertisements — GVWR, curb weight, gross combined vehicle weight and many others. To understand the differences between payload and towing capacity, you must put some of those other values into perspective.

1. What Does GVWR Mean?

The GVWR, gross vehicle weight rating, is one metric you will need to calculate to ensure you don’t cause long-lasting damage to your truck. You do not need to figure this value. Instead, you can find it on the plate affixed to the sidewall, which may be on the driver’s side door, or consult your owner’s manual.

This value measures how much your truck can carry inside it — the driver, passengers and cargo. The U.S. government classifies trucks into various classes based on the GVWR. Class 1 constitutes the smallest trucks weighing 6,000 pounds. Each level increases in varying increments up to Class 8, which includes trucks with GVWRs of greater than 33,000 pounds. The classifications help you to identify the type of vehicle you have.

Trucks with GVWRs up to 10,000 pounds are light-duty vehicles. Vehicles with greater than 10,000 pounds but less than 26,000 pounds for GVWR are considered to be medium-duty. Those above this weight are heavy-duty trucks. The higher the GVWR, the more your vehicle can carry in payload and towing.

2. What Is Curb Weight?

The curb weight of your truck is how much the vehicle weighs when empty. When determining maximum payload and towing capacities, you need to know the curb weight, which includes a full tank of gas and topped off fluids but no passengers or cargo. Your truck’s mass constitutes part of the GVWR, as does the load you carry. By removing the curb weight from the gross vehicle weight, you will find out how much additional weight your truck can handle.

3. What Is GCVWR?

Do not confuse GCVWR with GVWR. The former stands for gross combined vehicle weight rating while the latter represents the gross vehicle weight. You need the GCVWR to calculate towing capacity.

What is GCVWR?

GCVWR indicates the total amount for your loaded truck and trailer. Typically, this value exceeds the GVWR because your vehicle can tow much more than its overall weight. Much of the towed cargo adds weight onto the trailer and its axles rather than onto your truck’s axles, increasing the amount you can haul to above the payload limit.

4. What Is Trailer Tongue Weight?

Part of the payload capacity is tongue weight. This measurement indicates how much weight the towed load exerts on the truck’s tongue. It ranges from 10 to 15% of the total trailer weight. For example, if you have a single-axle eight-foot-long trailer, empty, the trailer weighs around 320 pounds. The trailer tongue weight would be:

  • 320 pounds x 0.1 = 32 pounds.

This tongue weight only accounts for an empty trailer. Don’t forget to add the mass of the cargo in or on the trailer before calculating the tongue weight if you will use the trailer for hauling. The tongue weight is how what you tow can impact the payload capacity of your truck.

5. Why These Numbers Are Important

You need to know whether to calculate truck payload vs. towing capacity when loading up your vehicle. Improperly secured trailers and cargo contributes to vehicle-related road debris. When AAA conducted a study of accidents from 2011 through 2014, it found 125 deaths and 9,805 injuries each year had direct connections to debris-related incidents. Out of every 1,000 crashes, 163 came from vehicle-related debris or fallen cargo.

If your cargo is not secured and within your truck’s carrying capacity, you could put undue stress on your vehicle’s suspension, transmission and engine. You could also hurt other drivers by causing accidents on the road.

6. Why You Can’t Use the Advertised Payload and Towing Capacities

Truck manufacturers will often calculate and advertise their truck’s payload and towing capacities. These values, however, are the maximums for when the vehicle has only a driver in it and no cargo. Such a scenario is not realistic for most drivers. You will likely have passengers or other goods inside the truck, such as tools for work. These extras add weight to the vehicle, lowering the actual payload and towing capacities.

Additionally, many manufacturers claim towing capacities for their trucks that the engine and tires would not realistically achieve, though the vehicle could technically support the load. To avoid falling for this type of data and ensuring your truck can actually move an advertised weight, look for a third-party approval of the truck makers’ claims.

The Society of Automotive Engineers, SAE, has a standard — the SAE J2807, that measures whether a truck can safely tow a specific load. The rigorous process the SAE puts trucks through includes multiple trials, such as the following:

  • Climbing: Trucks drive 11.4 miles, rising 3,000 feet with the air conditioner on. Dually trucks must maintain a speed of at least 35 mph, and standard pickups cannot go below 40 mph.
  • Acceleration: How well a truck can accelerate plays into how well it can pass while towing. Four-wheel vehicles have three marks to hit — 30 mph in 12 seconds, 60 mph in 30 sec and go from 40 mph to 60 mph in 18 sec.
  • Launching: Launching refers to how quickly a truck can move a load from a complete stop. While moving up a 12% grade, the test vehicle must climb 16 feet forward and backward five times in five minutes or less.

Truck brands that receive this group’s seal of approval for towing have vehicles that will reliably and safely pull the stated weights. However, even with the SAE J2807 standard, the towing weights are maximums. Do not exceed these values for towing. Also, calculate how your actual cab, bed and towing loads fit into the expected weights.

How to Calculate Truck Payload Capacity

How to Calculate Truck Payload CapacityWhile most manufacturers calculate payload capacity, you can also do the math yourself. Before getting to the math, though, you need to understand how manufacturers have used payload capacity values in the past and why those may not work with today’s vehicles.

If you see a truck advertised as a half-ton truck, the value indicates an approximation of the payload capacity — or, it did in the 1960s. Today’s trucks carry much more than that, and the definition of a half-ton truck indicates a light-duty vehicle.

To calculate the payload capacity, you need to know both the curb weight and the GVWR. Subtract the curb weight from the GVWR to find the payload capacity.

For example, if you have a light-duty truck with a GVWR of 9,000 pounds and a curb weight of 6,000 pounds, the payload capacity will be 3,000 pounds:

  • GVWR – curb weight = payload capacity
  • 9,000 pounds – 6,000 pounds = 3,000 pounds

This payload includes people and cargo without any towing added.

If you had a trailer, you also need to subtract the tongue weight from the GVWR. For this same example, if you had a trailer that weighs 2,000 pounds, the tongue weight would be 200 pounds. The total payload capacity will now drop to 2,800 pounds:

  • GVWR – curb weight – tongue weight = payload capacity when towing
  • 9,000 pounds – 6,000 pounds – 200 pounds = 2,800 pounds

When hauling cargo in your truck bed, consider the density of the material. For instance, one-half cubic yard of sand can weigh up to 1,500 pounds, but the same amount of mulch only weighs 400 pounds. Both take up the same volume, but they each weigh dramatically different amounts since their densities are different. The lesson to learn from these materials is just because something can fit into your truck bed does not mean that it will fit into your truck’s payload capacity, especially when you factor in the weights of passengers and other cargo into the equation.

Payload capacity will also decrease if you add any aftermarket options onto the truck. Subtract the weights of additions such as service bodies, towing attachments, enclosed bodies, platforms or dump bodies from the GVWR and the curb weight to calculate the payload capacity.

For instance, if you were to install a Reading SL service body for a single wheel, 98-inch bed and request steel lids, you will add 1,190 pounds to your truck. Installing this onto a 9,000-pound vehicle with a curb weight of 6,000 pounds will decrease your payload capacity to 1,810 pounds:

  • GVWR – curb weight – truck body additions = payload capacity with truck add-ons
  • 9,000 pounds – 6,000 pounds – 1,190 pounds = 1,810 pounds payload capacity

You can find the weight of truck additions in the specs for the service body. Total weight depends on the options you choose and the size of the add-on you need. Generally, steel weighs more than aluminum, and if you have a larger truck, your truck body will weigh more than if you have a small pickup. For customized additions, you will need to get the weight of the truck body from the dealer.

Calculating payload capacity only tells you how much weight you can put into the truck. It reflects the limits of the truck’s suspension system. However, with towing, much of the weight does not fall on the vehicle’s axles. Rather, it’s the trailer, which allows you to haul heavier loads than you can put inside the truck’s bed or cab.

How to Calculate Truck Towing Capacity

As with payload capacity, towing capacity is another calculation manufacturers make. However, they assume an empty vehicle with only a 150-pound driver. Calculating towing capacity on your own gives you the chance to reach a more realistic value based on all the people in the cab and any cargo.How to Calculate Truck Towing CapacityTo create a personalized towing capacity calculator, you need to know the GCVWR and the curb weight. Subtract the latter amount from the former to find the maximum towing capacity:

  • GCVWR – curb weight = maximum towing capacity

This calculation does not consider anything inside your truck other than full fluid levels. It does not account for passengers or cargo. If you want to find how much you can realistically tow, you need to subtract the amount of freight and passengers in the vehicle, too. The GCVWR includes both what you have inside the truck as well as what you carry behind it.

Use the formula to determine if you can carry the following gear and people in a truck with a curb weight of 6,000 pounds and a GCVWR of 15,000 pounds:

  • Three 150-pound passengers
  • A quarter-cord of firewood at 1,250 pounds
  • Tow a 2,800-pound car
  • With a 2,000-pound car trailer

The calculation for determining the towing capacity for a truck carrying the above gear requires you to subtract everything moved by the vehicle from the curb weight and the GCVWR:

  • GCVWR – curb weight – cargo – passengers ≥ total towing weight
  • 15,000 pounds – 6,000 pounds – 1,250 pounds – (3 people x 150 pounds each) = 7,300 pounds towing capacity
  • Car + trailer = total towing weight
  • 2,800 pounds + 2,000 pounds = 4,800 pounds total towed weight

Because the total towing weight of 4,800 pounds is less than the total towing capacity of 7,300 pounds, you can safely carry everything listed while still towing the car.

If you have any truck body additions installed, those will also affect the towing weight. Using the example of a Reading SL service body for a single wheel weight of 1,190 pounds, added onto the passengers, cargo, towed car and car hauler, you can calculate whether your truck can handle it. Subtract the body additions from the GCVWR, curb weight, cargo and passenger weights. The value should be higher than the towed weight:

  • GCVWR – curb weight – cargo – passengers – body additions ≥ total towing weight
  • 15,000 pounds – 6,000 pounds – 1,250 pounds – (3 people x 150 pounds each) – 1,190 pounds = 6,110 pounds towing capacity with body additions

Since the total towing weight still exceeds the sum of the car and trailer of 4,800 pounds, you can have this model of service body on your truck while carrying the stated cargo and passengers and towing a car on a trailer.

Customize Your Truck for Greater Productivity

Customize Your Truck for Greater ProductivityKnowing how much your truck can carry either in the payload or towing capacity will give you an idea of weight. However, you need to make the most of what you do bring by keeping it safe and secure. Instead of tossing everything into your truck bed, customize your ride to carry your equipment with service truck bodies.

Don’t forget to factor in the weight of any added service bodies on your truck when calculating payload and towing capacity. Ask us about loads of our service bodies to help you with this calculation. At Reading Body, we provide service bodies for a variety of industries including HVAC, landscaping, oil and gas, telecom, construction and utility. Visit one of our locations to see our products in person or talk to us about a customized design. By integrating a service body into your truck, you will make the most of the space you have.

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