Trailer Towing Payload and Capacity Calculator

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Trailer Towing Payload and Capacity Calculator

This calculator will estimate the towing capacity of your tow vehicle as well as the trailer loading on your tow vehicle.

Cells colored Green-ish are editable

Hitch Assembly Often described as the “hitch”, it is mounted to the tow vehicle (most often to the vehicle frame) and includes a hitch receiver, ball mount adapter, hitch ball and wiring harness.
Hitch Receiver The part of the hitch assembly that permits insertion of the ball mount adapter.
Drawbar (Ball Mount Adapter) A metal bar that carries the hitch ball and is inserted into the hitch receiver. There are some hitch assemblies available with permanently mounted or fixed ball mount adapter/drawbar.
Hitch Ball The steel ball bolted through the ball mount adapter or hole in the tow vehicle's rear bumper. The coupler on the trailer goes over the hitch ball.
Coupler Affixed to the trailer tongue, the coupler is a hollow metal stamping that covers the hitch ball.
Fifth-Wheel Hitch A special high platform with a coupling that mounts over the rear axle of the tow vehicle. Connect a vehicle and fifth wheel trailer with a coupling kingpin.
Fifth-Wheel Trailer (also see Gooseneck Trailer) One in which the king pin of the trailer attaches to a specially designed hitch mounted in the bed of a pickup truck. It is most popular with large travel, moving and horse trailers.
Gooseneck Trailer (also see Fifth-Wheel Trailer) The gooseneck trailer employs a ball socket hitch which attaches to a ball mounted in the bed of a pickup truck over the rear axle. The hitch mounts to the vehicle frame.
Gross Vehicle Weight (GVW) The total weight of the tow vehicle, including driver, passengers, any special equipment (options, accessories and up fitted equipment), cargo, fuel, coolant, trailer tongue weight, etc.
Gross Vehicle Weight Rating (GVWR) The maximum allowable total weight of the tow vehicle, including driver, passengers, any special equipment (options, accessories and up fitted equipment), cargo, fuel, coolant, trailer tongue weight, etc.
Gross Trailer Weight (GTW) The weight of the trailer plus all the cargo in it. This is measured by putting a fully loaded trailer on a scale. Maximum allowable weight of the trailer, plus its cargo.
Gross Combination Weight (GCW) Total weight of a fully equipped truck and trailer with cargo, driver and passengers, fuel, coolant, equipment, etc.
Gross Combination Weight Rating (GCWR) Maximum allowable gross combination weight.
Trailer Tongue Weight The downward force exerted on the hitch ball by the trailer coupler. In most cases, it should not be less than 10 percent of the trailer load or more than 15 percent. (Also see King Pin Weight below)
King Pin The main fastening member between a fifth-wheel hitch and a trailer.
King Pin Weight The downward force exerted on the king pin and pickup bed by fifth-wheel trailers (25 percent of the GTW)
Payload The sum resulting from subtraction of the curb weight from the gross vehicle weight rating (GVWR).

These are the five classifications for trailer weights and hitches:

Towing Classes

Class I - 2,000-pound maximum, Includes folding camping trailers and trailers for small boats, motorcycles and snowmobiles

Class II - 3,500-pound maximum, Single-axle, small to medium length (up to 18 feet) trailers

Class III - 5,000-pound maximum, Dual-axle or large single-axle trailers  Weight-distributing hitch not required, unless specified for the particular vehicle

Class IV - 5000-pound non- weight distributing, 12,900-pound maximum weight distributing, 1290 lbs. tongue weight, Largest travel trailers made for recreation, Weight-distributing hitch is required; as indicated by each weight classification

Class V - 17000 pound weight distributing or non- distributing, 1800 lbs. tongue weight, Equipment trailer 17,000-pound and over, Must be a fifth-wheel or gooseneck, or pintle hitch

Weight-Carrying Hitch
A weight-carrying hitch supports the trailer tongue weight, just as if it were luggage located at a hitch ball or some other connected point of the truck. These kinds of hitches are commonly used to tow small and medium sized trailers. There are three styles of weight-carrying hitches:

Fixed Drawbar – in which the ball platform is permanently welded to the hitch

Removable Drawbar – in which the ball platform is removable. This hitch is commonly referred to as a utility ball mount for Class III hookups

Weight-Distributing Hitch A weight-distributing system includes a receiver attached to the tow vehicle, plus a removable hitch head and spring bar assembly that fits into the receiver opening and hook up brackets that connect the spring bars to the trailer frame. This allows towing of trailers with greater tongue weights – typically Class IV categories – up to 12,000 pounds.

Fifth-Wheel Hitch A fifth-wheel hitch is a special platform with a coupling that mounts over the rear axle of the tow vehicle. It connects a vehicle and fifth wheel trailer with a coupling king pin. It is most popular with large travel, moving trailers.

Towing and Axle Ratios

On rear-wheel-drive vehicles, rear-axle ratio is an important part of a successful towing equation. It is expressed as a ratio between the drive shaft revolutions per minute and the rear axle's revolutions per minute. It is always given as a numerical shaft expression like 4.1:1. This means the small pinion gear at the end of the drive shaft must rotate 4.1 times for every single rotation of the rear axle / shafts. Each rear-axle ratio in the spectrum of those offered has a plus and minus. A ratio that is "low" in the number of drive shaft rotations for every axle rotation results in lower engine rpm and in better fuel economy, longer engine life and quieter running. But it won't be good for quick acceleration, climbing grades, carrying loads or pulling a trailer. A "high" ratio, one with a high number of drive shaft turns like the 4.1:1 example above, is better for quick acceleration, climbing grades, carrying loads or pulling a trailer. However, it results in lower fuel economy and is noisier when running at high vehicle speeds. For any application, it is best to determine a ratio that will enable your Ram vehicle to pull a trailer with the engine operating closest to its optimal power range - where peak torque and peak horsepower meet on the engine power curve chart. This maximizes power, efficiency fuel economy. It is best to determine a ratio that will give good trailer towing power without handicapping non-towing performance too severely.

Diesel Exhaust brake or "Jake Brake" Usage An exhaust brake or "Jake Brake" is recommended for Dodge 3500 Pickup and Chassis Cab models pulling a trailer weight of 10,000 pounds or more.

Fifth-wheel Hitch Requirement

Calculation of the GTW ratings is intended to provide acceptable performance for normal conditions of temperature, grade, and altitude. Extreme conditions will require selection of a higher axle ratio and/or a higher powered engine. These ratings must be decreased by the weight of any optional equipment, trailer hitch, cargo in the tow vehicle, and passengers other than the driver. To determine the GTW, subtract the tow vehicle curb weight and 150 pounds (allowance for the driver) from the GCWR. The maximum allowable trailer weight for vehicles with max option content are listed in the “Model Lineup” sections of each vehicle in the Body Builder's Guide. A maximum engine cooling option may be required to achieve the maximum trailer weight rating and GCWR.

Caution:

When hauling cargo or towing a trailer, do not overload the vehicle or trailer. Overloading can cause a loss of control, poor performance or damage to brakes, axle, engine, transmission, steering, suspension, body structure or tires.

Tongue weight

To determine the maximum trailer tongue weight, multiply the gross trailer weight (GTW) by 15 percent. The ideal tongue weight should be about 13 percent. However, the maximum tongue weight on a class III bumper hitch is limited to 500 lbs. and a class IV receiver hitch is limited to 1,045 lbs. For maximum king pin weight on fifth-wheel applications, multiply the GTW by 25 percent.

References

SAE J-2807, Surface Vehicle Recommended Practice, Performance Requirements for Determining Tow-Vehicle Gross Combination Weight Rating and Trailer Weight Rating
SAE J684 Trailer Couplings, Hitches, and Safety Chains - Automotive Type
SAE J2638 Fifth Wheel and Gooseneck Attachment Performance Up to 13608/kg (30000/lb) Trailer Weight