How to Calculate Tongue Weight

Trailer Tongue Weight Calculator

Use this calculator to estimate your trailer's tongue weight based on its empty weight, center of gravity, and cargo distribution. Maintaining proper tongue weight (typically 10-15% of the Gross Trailer Weight) is crucial for safe towing, preventing trailer sway, and ensuring stable handling.

Trailer Specifications

Enter a positive value if the empty trailer's CG is forward of the axle, negative if behind. (e.g., 20 for 20 inches forward)

This is the total length from the axle to the center of the hitch ball when connected. Must be positive.

Cargo Loading

Enter the weight and distance from the axle for up to three cargo items. Positive distance means the item's center is forward of the axle, negative means behind.

function calculateTongueWeight() { var emptyTrailerWeight = parseFloat(document.getElementById('emptyTrailerWeight').value); var emptyTrailerCGFromAxle = parseFloat(document.getElementById('emptyTrailerCGFromAxle').value); var axleToCouplerDistance = parseFloat(document.getElementById('axleToCouplerDistance').value); var cargo1Weight = parseFloat(document.getElementById('cargo1Weight').value); var cargo1Distance = parseFloat(document.getElementById('cargo1Distance').value); var cargo2Weight = parseFloat(document.getElementById('cargo2Weight').value); var cargo2Distance = parseFloat(document.getElementById('cargo2Distance').value); var cargo3Weight = parseFloat(document.getElementById('cargo3Weight').value); var cargo3Distance = parseFloat(document.getElementById('cargo3Distance').value); var resultDiv = document.getElementById('result'); resultDiv.innerHTML = "; // Clear previous results // Input validation if (isNaN(emptyTrailerWeight) || emptyTrailerWeight < 0 || isNaN(emptyTrailerCGFromAxle) || isNaN(axleToCouplerDistance) || axleToCouplerDistance <= 0) { resultDiv.innerHTML = 'Please enter valid positive numbers for Empty Trailer Weight and Axle to Coupler Distance. Empty Trailer CG Distance can be negative.'; return; } // Default cargo values to 0 if not entered or invalid if (isNaN(cargo1Weight) || cargo1Weight < 0) cargo1Weight = 0; if (isNaN(cargo1Distance)) cargo1Distance = 0; if (isNaN(cargo2Weight) || cargo2Weight < 0) cargo2Weight = 0; if (isNaN(cargo2Distance)) cargo2Distance = 0; if (isNaN(cargo3Weight) || cargo3Weight < 0) cargo3Weight = 0; if (isNaN(cargo3Distance)) cargo3Distance = 0; // Calculate moments about the axle var momentEmpty = emptyTrailerWeight * emptyTrailerCGFromAxle; var momentCargo1 = cargo1Weight * cargo1Distance; var momentCargo2 = cargo2Weight * cargo2Distance; var momentCargo3 = cargo3Weight * cargo3Distance; var totalMoment = momentEmpty + momentCargo1 + momentCargo2 + momentCargo3; // Calculate Tongue Weight var calculatedTongueWeight = totalMoment / axleToCouplerDistance; // Calculate Gross Trailer Weight (GTW) var grossTrailerWeight = emptyTrailerWeight + cargo1Weight + cargo2Weight + cargo3Weight; // Calculate ideal tongue weight range (10-15% of GTW) var minIdealTongueWeight = 0.10 * grossTrailerWeight; var maxIdealTongueWeight = 0.15 * grossTrailerWeight; var statusMessage = ''; var statusColor = 'black'; if (calculatedTongueWeight maxIdealTongueWeight) { statusMessage = 'Your calculated tongue weight is TOO HIGH. This can overload your tow vehicle\'s rear axle and reduce steering control.'; statusColor = 'red'; } else { statusMessage = 'Your calculated tongue weight is within the ideal range for safe towing.'; statusColor = 'green'; } resultDiv.innerHTML = '

Calculation Results:

' + 'Calculated Tongue Weight: ' + calculatedTongueWeight.toFixed(2) + ' lbs' + 'Gross Trailer Weight (GTW): ' + grossTrailerWeight.toFixed(2) + ' lbs' + 'Ideal Tongue Weight Range (10-15% of GTW): ' + minIdealTongueWeight.toFixed(2) + ' lbs – ' + maxIdealTongueWeight.toFixed(2) + ' lbs' + 'Status: ' + statusMessage + " + 'Note: This calculation is an estimate. Always verify with a tongue weight scale and ensure your tow vehicle\'s hitch and axle ratings are not exceeded.'; }

Understanding Trailer Tongue Weight for Safe Towing

Trailer tongue weight (TW) is one of the most critical factors for safe and stable towing. It refers to the downward force exerted by the trailer's coupler onto the hitch ball of the tow vehicle. Proper tongue weight ensures that the trailer tracks smoothly behind the tow vehicle, preventing dangerous sway and maintaining control.

Why is Tongue Weight So Important?

• Prevents Trailer Sway: The most common and dangerous issue caused by improper tongue weight is trailer sway. If the tongue weight is too low, the trailer can become unstable, causing it to wag back and forth, especially at higher speeds or in windy conditions. This can quickly lead to loss of control.
• Maintains Steering Control: Too much tongue weight can overload the tow vehicle's rear axle, lifting the front wheels slightly. This reduces the weight on the front tires, negatively impacting steering, braking, and overall vehicle control.
• Optimizes Braking Performance: Correct tongue weight helps distribute the load evenly, allowing both the tow vehicle and trailer brakes to operate effectively.
• Reduces Wear and Tear: Proper weight distribution minimizes undue stress on the tow vehicle's suspension, tires, and frame, extending their lifespan.

The Ideal Tongue Weight Range

As a general rule of thumb, the tongue weight should be between 10% and 15% of the Gross Trailer Weight (GTW). The GTW is the total weight of the fully loaded trailer, including all cargo, water, and supplies.

• Below 10%: Too little tongue weight. This is the primary cause of trailer sway. The trailer acts like a pendulum, swinging uncontrollably.
• Above 15%: Too much tongue weight. This can overload the tow vehicle's rear suspension, potentially causing the front wheels to lift, reducing steering and braking effectiveness. It can also exceed the hitch receiver's weight rating.

How to Calculate Tongue Weight (The Physics Behind the Calculator)

While a tongue weight scale provides a direct measurement, this calculator uses a physics-based approach to estimate tongue weight by considering the moments (rotational forces) created by the trailer's components and cargo around its axle. Think of the trailer axle as a pivot point.

The formula essentially balances the rotational forces:

Tongue Weight = (Sum of all Moments about the Axle) / (Distance from Axle to Coupler)

A "moment" is calculated by multiplying a weight by its distance from the axle. Weights placed forward of the axle create a positive moment (pushing the tongue down), while weights placed behind the axle create a negative moment (lifting the tongue).

• Empty Trailer Weight & CG: The empty trailer itself has a weight and a center of gravity (CG). If its CG is forward of the axle, it contributes to tongue weight. If it's behind, it reduces it.
• Cargo Weight & Distance: Each item of cargo contributes to or subtracts from the tongue weight based on its weight and its position relative to the axle. Moving heavy items even a few inches can significantly alter the tongue weight.
• Axle to Coupler Distance: This is the leverage arm. A longer distance means less tongue weight for the same total moment, and vice-versa.

Adjusting Your Tongue Weight

If your calculated tongue weight falls outside the ideal 10-15% range, you'll need to adjust your cargo. The most effective way to do this is by:

• Moving heavy items: Shifting heavy cargo forward increases tongue weight; shifting it backward decreases tongue weight.
• Distributing weight: Try to load heavier items over or slightly forward of the trailer's axle.
• Adding or removing items: If adjustments aren't enough, you may need to add or remove cargo.

Final Verification

While this calculator provides a valuable estimate for planning your load, it's always recommended to verify your actual tongue weight using a dedicated tongue weight scale before hitting the road. Also, ensure that your tow vehicle's hitch receiver, ball mount, and rear axle ratings are not exceeded by the actual tongue weight and Gross Trailer Weight.