Max Trailer Weight Calculator

Max Trailer Weight Calculator – Calculate Towing Capacity Safely :root { –primary-color: #004a99; –success-color: #28a745; –background-color: #f8f9fa; –text-color: #333; –card-background: #ffffff; –border-color: #ddd; –shadow-color: rgba(0, 0, 0, 0.1); } body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: var(–background-color); color: var(–text-color); margin: 0; padding: 0; line-height: 1.6; display: flex; justify-content: center; padding: 20px 0; } .container { width: 100%; max-width: 960px; background-color: var(–card-background); padding: 30px; border-radius: 8px; box-shadow: 0 4px 15px var(–shadow-color); margin: 10px; } h1, h2, h3 { color: var(–primary-color); margin-bottom: 15px; } h1 { text-align: center; margin-bottom: 30px; font-size: 2.2em; } .calc-section, .article-section { margin-bottom: 40px; padding-bottom: 20px; border-bottom: 1px solid var(–border-color); } .calc-section:last-child, .article-section:last-child { border-bottom: none; 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Max Trailer Weight Calculator

Calculate Your Vehicle's Max Trailer Weight

Ensure safe towing by understanding your vehicle's limitations. Enter the required information below.

The weight of your vehicle with all standard equipment, full fluids, and a driver (typically 165-180 lbs).
The maximum weight your vehicle can carry in passengers and cargo (found on doorjamb sticker).
10% (Common for conventional trailers) 15% (Common for fifth-wheel/gooseneck) 12% (Mid-range) The percentage of the trailer's weight that rests on the hitch. Check your hitch manual.
The maximum weight your hitch can support. Often found on the hitch receiver or vehicle's towing guide.

Your Towing Capacity Results

Formula Used: Maximum Trailer Weight = (Maximum Allowed Tongue Weight / Tongue Weight Percentage)

Assumptions: This calculation assumes your vehicle's payload capacity is sufficient for the combined weight of passengers, cargo, and tongue weight. It also assumes the trailer's tongue weight will be within the specified percentage of its total weight.
Results copied!

Trailer Weight vs. Tongue Weight

What is Max Trailer Weight?

The term "Max Trailer Weight" refers to the absolute maximum weight that a specific vehicle is designed and rated to safely tow. This is not just about engine power; it encompasses the entire vehicle's structural integrity, braking system, suspension, and cooling capabilities. Exceeding your vehicle's max trailer weight rating can lead to dangerous driving conditions, accelerated wear and tear on your vehicle, and potentially void your warranty or insurance coverage. Understanding and respecting this limit is paramount for safe towing.

Who Should Use a Max Trailer Weight Calculator?

Anyone planning to tow a trailer, regardless of its size or type, should be aware of their vehicle's maximum trailer weight capacity. This includes individuals who:

  • Own or plan to purchase recreational vehicles like travel trailers, fifth wheels, or pop-up campers.
  • Need to transport equipment or materials for work or hobbies using a utility trailer, car hauler, or equipment trailer.
  • Are using their vehicle for towing services, such as moving boats, ATVs, or horses.
  • Are considering purchasing a new vehicle and want to ensure it meets their towing needs.

Common Misconceptions about Max Trailer Weight

  • "If my vehicle can move it, it's fine.": This ignores critical factors like braking distance, stability, suspension stress, and overheating.
  • "Towing capacity is the same as trailer weight.": Towing capacity is the *total* weight the vehicle can pull. Trailer weight refers to the trailer itself. Crucially, the *tongue weight* (the downward force on the hitch) is a significant portion of this that must be accounted for within the vehicle's payload capacity.
  • "All trucks of the same model can tow the same amount.": Different engine options, drivetrain configurations (2WD vs. 4WD), and trim levels within the same vehicle model can have significantly different towing capacities.

Max Trailer Weight Formula and Mathematical Explanation

The core principle behind calculating the maximum trailer weight capacity revolves around the vehicle's ability to support the load, primarily through its hitch system. While the vehicle's overall towing capacity rating is the ultimate limit, a practical way to determine a safe trailer weight involves considering the hitch's limitations and the distribution of weight. A common method focuses on the maximum allowed tongue weight.

The Basic Calculation:

The most straightforward calculation for the maximum trailer weight is derived from the maximum tongue weight your hitch can handle and the typical percentage of trailer weight that tongue weight represents.

Maximum Trailer Weight = (Maximum Allowed Tongue Weight / Tongue Weight Percentage)

Variable Explanations:

  • Vehicle Curb Weight: This is the weight of the vehicle itself, fully equipped with operating fluids (fuel, oil, coolant, etc.) but without passengers or cargo. It's the base weight of the tow vehicle.
  • Payload Capacity: This is the maximum weight your vehicle can carry in passengers, cargo, and accessories. Critically, the tongue weight of the trailer is considered part of this payload.
  • Tongue Weight Percentage: This is the proportion of the trailer's total weight that presses down on the vehicle's hitch. It's typically expressed as a percentage. For conventional trailers, 10-15% is common. For fifth-wheel or gooseneck trailers, it's often 15-25%.
  • Maximum Allowed Tongue Weight: This is the maximum downward force your specific hitch receiver or towing system is rated to support. This is often listed on the hitch itself or in the vehicle's towing guide.

Variables Table:

Variable Meaning Unit Typical Range
Vehicle Curb Weight Weight of the tow vehicle with fluids, no passengers/cargo. lbs (or kg) 2,000 – 8,000+ lbs
Payload Capacity Max weight of passengers, cargo, and tongue weight. lbs (or kg) 500 – 5,000+ lbs
Tongue Weight Percentage % of trailer weight pressing on the hitch. % 10% – 25%
Maximum Allowed Tongue Weight Max force the hitch can safely handle. lbs (or kg) 200 – 3,000+ lbs
Maximum Trailer Weight The calculated maximum weight of the trailer. lbs (or kg) Varies widely based on tow vehicle.

Important Note: The calculated maximum trailer weight using the tongue weight method should NEVER exceed the vehicle's official Gross Combined Weight Rating (GCWR) minus the vehicle's curb weight and any added equipment. It also must not result in a tongue weight that exceeds the vehicle's payload capacity when combined with passengers and cargo.

Practical Examples (Real-World Use Cases)

Example 1: Towing a Small Travel Trailer

Sarah is looking to buy a small travel trailer for weekend getaways. Her SUV has the following specifications:

  • Vehicle Curb Weight: 4,800 lbs
  • Payload Capacity: 1,600 lbs
  • Maximum Allowed Tongue Weight (from hitch): 600 lbs
  • Recommended Tongue Weight Percentage: 12%

Calculation:

Maximum Trailer Weight = (Maximum Allowed Tongue Weight / Tongue Weight Percentage)

Maximum Trailer Weight = (600 lbs / 0.12) = 5,000 lbs

Intermediate Values:

  • Calculated Tongue Weight at Max Trailer Weight: 600 lbs

Interpretation: Sarah's SUV, based on its hitch capacity, can tow a trailer weighing up to 5,000 lbs. However, she must ensure the tongue weight (600 lbs) doesn't push her total payload (passengers + cargo + 600 lbs) over the 1,600 lb limit. If she plans to carry 300 lbs of passengers and gear, she has 1,600 – 300 – 600 = 700 lbs of remaining payload capacity, which is sufficient.

Example 2: Towing a Car Hauler with a Pickup Truck

John needs to transport his project car using a car hauler trailer with his pickup truck. His truck's details are:

  • Vehicle Curb Weight: 5,500 lbs
  • Payload Capacity: 2,100 lbs
  • Maximum Allowed Tongue Weight (from hitch): 1,000 lbs
  • Recommended Tongue Weight Percentage: 15% (for a heavier trailer)

Calculation:

Maximum Trailer Weight = (Maximum Allowed Tongue Weight / Tongue Weight Percentage)

Maximum Trailer Weight = (1000 lbs / 0.15) = 6,667 lbs

Intermediate Values:

  • Calculated Tongue Weight at Max Trailer Weight: 1,000 lbs

Interpretation: Based on his hitch, John's truck can tow trailers up to approximately 6,667 lbs. He needs to consider the weight of the trailer plus the car. If the trailer itself weighs 2,000 lbs, the car can weigh up to 4,667 lbs. The tongue weight will be 1,000 lbs. If John plans to carry himself (180 lbs) and some tools (100 lbs), his total payload is 180 + 100 + 1000 = 1,280 lbs. This is well within his 2,100 lb payload capacity.

How to Use This Max Trailer Weight Calculator

  1. Enter Vehicle Curb Weight: Find this information in your vehicle's owner's manual or often on a sticker inside the driver's doorjamb. It's the weight of your truck or SUV when empty.
  2. Enter Payload Capacity: This crucial number, also found on the driver's doorjamb sticker, indicates the maximum weight your vehicle can carry (passengers, cargo, and trailer tongue weight combined).
  3. Select Tongue Weight Percentage: Choose the appropriate percentage based on your trailer type and hitch. 10-15% is standard for conventional trailers, while 15-25% is typical for fifth-wheel or gooseneck trailers. Consult your hitch manufacturer or towing guide.
  4. Enter Maximum Allowed Tongue Weight: This is the maximum downward force your hitch receiver or towing system can safely handle. It's usually stamped on the hitch itself or listed in your vehicle's towing guide.
  5. Click 'Calculate': The calculator will process your inputs.

How to Read the Results:

  • Primary Result (Max Trailer Weight): This is the maximum weight of a trailer your vehicle can *potentially* tow, based on the calculated tongue weight capacity.
  • GVWR (Gross Vehicle Weight Rating): This is the maximum operating weight of the tow vehicle itself.
  • Max Payload for Towing: This indicates how much of your vehicle's payload capacity is consumed by the trailer's tongue weight at the calculated maximum trailer weight. You must ensure this, plus passengers and cargo, does not exceed your vehicle's Payload Capacity.
  • Calculated Tongue Weight: This is the specific downward force on your hitch when towing the calculated max trailer weight.

Decision-Making Guidance:

Always compare the calculated Maximum Trailer Weight to your vehicle's *official* towing capacity rating (found in the owner's manual). Your safe towing limit is the *lower* of the two numbers. Furthermore, always ensure that the calculated tongue weight, combined with the weight of your passengers and any cargo inside the vehicle, does not exceed your vehicle's Payload Capacity.

Key Factors That Affect Max Trailer Weight Results

While the calculator provides a crucial estimate, several real-world factors influence the actual safe towing capacity and the performance of your setup.

  1. Vehicle's Official Towing Capacity:

    This is the manufacturer's rated limit for the entire towing setup (vehicle + trailer). It considers the engine, transmission, brakes, cooling system, and chassis. Your calculated max trailer weight should never exceed this official rating. The official rating is often the most limiting factor.

  2. Gross Vehicle Weight Rating (GVWR):

    This is the maximum loaded weight of the tow vehicle itself (curb weight + passengers + cargo). The tongue weight of the trailer counts towards this. Exceeding the GVWR compromises the vehicle's stability and braking.

  3. Gross Combined Weight Rating (GCWR):

    This is the maximum allowable combined weight of the fully loaded tow vehicle AND the fully loaded trailer. It's crucial to stay below this limit to prevent drivetrain and brake strain.

  4. Payload Capacity:

    As mentioned, this limits how much weight you can add to the tow vehicle. The trailer's tongue weight is a significant portion of this. Overloading payload drastically affects handling and braking.

  5. Hitch Rating:

    The calculator uses the hitch's tongue weight rating. Ensure your hitch is correctly installed and rated for your intended load. Exceeding the hitch rating can lead to catastrophic failure.

  6. Trailer Type and Load Distribution:

    A well-balanced trailer with 10-15% tongue weight is more stable. An improperly loaded trailer, even if within weight limits, can cause dangerous sway.

  7. Driving Conditions and Terrain:

    Towing in mountains, strong crosswinds, or adverse weather requires a greater margin of safety. Always reduce speed and increase following distance. Towing capacity ratings are typically for ideal, flat conditions.

  8. Braking Systems:

    Trailers over a certain weight (often 3,000 lbs) require their own braking system. Ensure your trailer brakes are functioning correctly and are properly adjusted.

Frequently Asked Questions (FAQ)

What is the difference between towing capacity and tongue weight?

Towing capacity is the maximum weight your vehicle can pull. Tongue weight is the downward force the trailer exerts on your hitch, and it counts towards your vehicle's payload capacity.

Can I tow a trailer that weighs exactly my vehicle's towing capacity?

Ideally, no. You should aim to tow well below the maximum capacity. Always leave a safety margin. Also, ensure the tongue weight doesn't overload your vehicle's payload capacity.

Where can I find my vehicle's curb weight and payload capacity?

These are typically found on a sticker on the driver's side doorjamb. Curb weight might also be in the owner's manual. Payload capacity is often listed as "The combined weight of occupants and cargo should never exceed XXXX lbs (or kg)."

What happens if I exceed my max trailer weight?

Exceeding limits can lead to loss of control, brake failure, suspension damage, transmission overheating, and accidents. It can also void your vehicle warranty and insurance.

Does the weight of passengers and cargo matter when towing?

Yes, absolutely. The combined weight of passengers, cargo in the tow vehicle, and the trailer's tongue weight must not exceed the vehicle's payload capacity. This is a critical safety limit.

How does a fifth-wheel or gooseneck hitch change things?

These hitches mount in the truck bed and typically allow for a higher tongue weight percentage (15-25%) and a higher overall towing capacity compared to bumper-mounted hitches. This allows for towing heavier trailers like large fifth-wheel RVs.

Do I need trailer brakes?

Most jurisdictions require trailers weighing over 3,000 lbs to have their own braking system. Even if not legally required, brakes are highly recommended for trailers over 1,500-2,000 lbs to ensure safe stopping distances.

Can I upgrade my vehicle's towing capacity?

While you can add aftermarket towing accessories like weight-distributing hitches or upgraded suspension components to improve stability and handling, you cannot legally or safely increase the manufacturer's *rated* towing capacity. Always adhere to the manufacturer's specifications.

Related Tools and Internal Resources

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var vehicleCurbWeightInput = document.getElementById('vehicleCurbWeight'); var payloadCapacityInput = document.getElementById('payloadCapacity'); var tongueWeightPercentageInput = document.getElementById('tongueWeightPercentage'); var maxTongueWeightInput = document.getElementById('maxTongueWeight'); var errorVehicleCurbWeight = document.getElementById('error-vehicleCurbWeight'); var errorPayloadCapacity = document.getElementById('error-payloadCapacity'); var errorTongueWeightPercentage = document.getElementById('error-tongueWeightPercentage'); var errorMaxTongueWeight = document.getElementById('error-maxTongueWeight'); var resultContainer = document.getElementById('result-container'); var primaryResultDiv = document.getElementById('primary-result'); var gvwrSpan = document.getElementById('gvwr'); var maxPayloadForTowingSpan = document.getElementById('maxPayloadForTowing'); var calculatedTongueWeightSpan = document.getElementById('calculatedTongueWeight'); var towingCapacityChart = document.getElementById('towingCapacityChart'); var chartInstance = null; function validateInput(element, errorElement, min, max) { var value = parseFloat(element.value); var isValid = true; if (isNaN(value)) { errorElement.textContent = "Please enter a valid number."; errorElement.style.display = 'block'; isValid = false; } else if (value max) { errorElement.textContent = "Value cannot exceed " + max + "."; errorElement.style.display = 'block'; isValid = false; } else { errorElement.textContent = ""; errorElement.style.display = 'none'; } return isValid; } function calculateMaxTrailerWeight() { var vehicleCurbWeight = parseFloat(vehicleCurbWeightInput.value); var payloadCapacity = parseFloat(payloadCapacityInput.value); var tongueWeightPercentage = parseFloat(tongueWeightPercentageInput.value) / 100; var maxTongueWeight = parseFloat(maxTongueWeightInput.value); var valid = true; valid = validateInput(vehicleCurbWeightInput, errorVehicleCurbWeight, 100) && valid; valid = validateInput(payloadCapacityInput, errorPayloadCapacity, 100) && valid; valid = validateInput(maxTongueWeightInput, errorMaxTongueWeight, 100) && valid; // Tongue weight percentage is a select, so we assume it's valid unless explicitly handled if (!valid) { resultContainer.style.display = 'none'; return; } // Calculate Max Trailer Weight based on Tongue Weight var calculatedMaxTrailerWeight = 0; if (tongueWeightPercentage > 0) { calculatedMaxTrailerWeight = maxTongueWeight / tongueWeightPercentage; } else { // Handle case where percentage is 0 or invalid to avoid division by zero calculatedMaxTrailerWeight = 0; } calculatedMaxTrailerWeight = Math.round(calculatedMaxTrailerWeight); // Calculate intermediate values var calculatedTongueWeight = Math.round(calculatedMaxTrailerWeight * tongueWeightPercentage); var effectiveGVWR = Math.round(vehicleCurbWeight + payloadCapacity); // Approximate GVWR var maxPayloadConsumedByTongue = calculatedTongueWeight; // Display results primaryResultDiv.textContent = calculatedMaxTrailerWeight.toLocaleString() + " lbs"; gvwrSpan.innerHTML = "Approx. GVWR: " + effectiveGVWR.toLocaleString() + " lbs (Vehicle Curb Weight + Payload Capacity)"; maxPayloadForTowingSpan.innerHTML = "Payload Used by Tongue Weight: " + maxPayloadConsumedByTongue.toLocaleString() + " lbs"; calculatedTongueWeightSpan.innerHTML = "Calculated Tongue Weight: " + calculatedTongueWeight.toLocaleString() + " lbs"; resultContainer.style.display = 'block'; // Update Chart updateChart(vehicleCurbWeight, payloadCapacity, maxTongueWeight, tongueWeightPercentage); } function resetCalculator() { vehicleCurbWeightInput.value = "4500"; payloadCapacityInput.value = "1500"; tongueWeightPercentageInput.value = "12"; // Default to 12% maxTongueWeightInput.value = "540"; // Default based on 4500*0.12 document.querySelectorAll('.error-message').forEach(function(el) { el.textContent = ""; el.style.display = 'none'; }); resultContainer.style.display = 'none'; if (chartInstance) { chartInstance.destroy(); chartInstance = null; } } function copyResults() { var resultText = "Max Trailer Weight Calculator Results:\n\n"; resultText += "Primary Result (Max Trailer Weight): " + primaryResultDiv.textContent + "\n"; resultText += gvwrSpan.textContent.replace('Approx. ', ") + "\n"; resultText += maxPayloadForTowingSpan.textContent + "\n"; resultText += calculatedTongueWeightSpan.textContent + "\n\n"; resultText += "Key Assumptions:\n"; resultText += "- Tongue Weight Percentage: " + document.getElementById('tongueWeightPercentage').options[document.getElementById('tongueWeightPercentage').selectedIndex].text.split(' ')[0] + "%\n"; resultText += "- Vehicle Curb Weight: " + vehicleCurbWeightInput.value + " lbs\n"; resultText += "- Payload Capacity: " + payloadCapacityInput.value + " lbs\n"; resultText += "- Max Tongue Weight: " + maxTongueWeightInput.value + " lbs\n"; var textArea = document.createElement("textarea"); textArea.value = resultText; document.body.appendChild(textArea); textArea.select(); try { var successful = document.execCommand('copy'); var msg = successful ? 'Results copied!' : 'Copying failed'; var feedbackDiv = document.querySelector('.copy-feedback'); feedbackDiv.textContent = msg; feedbackDiv.style.display = 'block'; setTimeout(function() { feedbackDiv.style.display = 'none'; }, 3000); } catch (err) { console.error('Unable to copy', err); var feedbackDiv = document.querySelector('.copy-feedback'); feedbackDiv.textContent = 'Copying failed'; feedbackDiv.style.display = 'block'; setTimeout(function() { feedbackDiv.style.display = 'none'; }, 3000); } document.body.removeChild(textArea); } function updateChart(vehicleCurbWeight, payloadCapacity, maxTongueWeight, tongueWeightPercentage) { if (chartInstance) { chartInstance.destroy(); } var ctx = towingCapacityChart.getContext('2d'); var labels = []; var trailerWeights = []; var correspondingTongueWeights = []; var maxPossibleTrailerWeightFromHitch = maxTongueWeight / tongueWeightPercentage; var maxTrailerWeightBasedOnPayload = payloadCapacity / tongueWeightPercentage; // Max trailer weight if *all* payload is tongue weight // Determine a sensible max for the chart x-axis var chartMaxTrailerWeight = Math.max(maxPossibleTrailerWeightFromHitch, maxTrailerWeightBasedOnPayload, 5000); chartMaxTrailerWeight = Math.min(chartMaxTrailerWeight, 10000); // Cap at 10,000 for readability for (var i = 0; i 0) { // Already captured } else if (weight > maxPossibleTrailerWeightFromHitch && i === 10 && maxPossibleTrailerWeightFromHitch > 0) { // Ensure the max hitch capacity point is visible if it's the max on the chart } } // Add the actual max hitch calculation point if not already there if (!trailerWeights.includes(Math.round(maxPossibleTrailerWeightFromHitch)) && maxPossibleTrailerWeightFromHitch > 0) { labels.push(Math.round(maxPossibleTrailerWeightFromHitch).toLocaleString() + " lbs"); trailerWeights.push(Math.round(maxPossibleTrailerWeightFromHitch)); correspondingTongueWeights.push(maxTongueWeight); // This should be exactly maxTongueWeight } // Sort data for chart var combinedData = trailerWeights.map(function(weight, index) { return { weight: weight, tongue: correspondingTongueWeights[index] }; }); combinedData.sort(function(a, b) { return a.weight – b.weight; }); labels = combinedData.map(function(item) { return item.weight.toLocaleString() + " lbs"; }); trailerWeights = combinedData.map(function(item) { return item.weight; }); correspondingTongueWeights = combinedData.map(function(item) { return item.tongue; }); chartInstance = new Chart(ctx, { type: 'line', data: { labels: labels, datasets: [{ label: 'Trailer Weight', data: trailerWeights, borderColor: 'rgb(75, 192, 192)', tension: 0.1, fill: false, pointRadius: 5, pointBackgroundColor: 'rgb(75, 192, 192)' }, { label: 'Resulting Tongue Weight', data: correspondingTongueWeights, borderColor: 'rgb(255, 99, 132)', tension: 0.1, fill: false, pointRadius: 5, pointBackgroundColor: 'rgb(255, 99, 132)' }] }, options: { responsive: true, maintainAspectRatio: false, scales: { y: { beginAtZero: true, title: { display: true, text: 'Weight (lbs)' }, max: Math.max(payloadCapacity + 500, maxTongueWeight + 500, 2000) // Adjust max y-axis based on payload and tongue weight }, x: { title: { display: true, text: 'Trailer Weight (lbs)' } } }, plugins: { tooltip: { callbacks: { label: function(context) { var label = context.dataset.label || "; if (label) { label += ': '; } if (context.parsed.y !== null) { label += context.parsed.y.toLocaleString() + ' lbs'; } return label; } } }, legend: { position: 'top', } }, // Add a line for max allowed tongue weight beforeDraw: function(chart) { var xScale = chart.scales.x; var yScale = chart.scales.y; var ctx = chart.ctx; // Line for Max Allowed Tongue Weight if (maxTongueWeight > 0) { ctx.save(); ctx.beginPath(); ctx.moveTo(xScale.getPixelForValue(0), yScale.getPixelForValue(maxTongueWeight)); ctx.lineTo(xScale.width + xScale.left, yScale.getPixelForValue(maxTongueWeight)); ctx.lineWidth = 2; ctx.strokeStyle = 'rgba(255, 99, 132, 0.5)'; // Semi-transparent red ctx.stroke(); ctx.restore(); // Label for the max tongue weight line ctx.fillStyle = 'rgba(255, 99, 132, 0.7)'; ctx.font = '12px Arial'; ctx.textAlign = 'left'; ctx.fillText('Max Tongue Weight (' + maxTongueWeight.toLocaleString() + ' lbs)', xScale.right + 5, yScale.getPixelForValue(maxTongueWeight)); } // Line for Payload Capacity (representing max trailer weight if all payload is tongue weight) if (maxTrailerWeightBasedOnPayload > 0 && maxTrailerWeightBasedOnPayload xScale.width / 2) { // If line is on the right half, align right ctx.textAlign = 'right'; xPos = xScale.getPixelForValue(maxTrailerWeightBasedOnPayload); } else { // Otherwise align left ctx.textAlign = 'left'; xPos = xScale.getPixelForValue(maxTrailerWeightBasedOnPayload) + 5; } ctx.fillText('Max TW based on Payload (' + Math.round(maxTrailerWeightBasedOnPayload).toLocaleString() + ' lbs)', xPos, yPos); } } } }); } function toggleFaq(element) { var p = element.nextElementSibling; if (p.style.display === "block") { p.style.display = "none"; } else { p.style.display = "block"; } } // Initial calculation on load if inputs have default values document.addEventListener('DOMContentLoaded', function() { // Set a default value for maxTongueWeight based on initial inputs var initialVehicleCurbWeight = parseFloat(vehicleCurbWeightInput.value); var initialPayloadCapacity = parseFloat(payloadCapacityInput.value); var initialTongueWeightPercentage = parseFloat(tongueWeightPercentageInput.value) / 100; var defaultMaxTongueWeight = Math.round(initialPayloadCapacity * initialTongueWeightPercentage); maxTongueWeightInput.value = defaultMaxTongueWeight; // Trigger initial calculation calculateMaxTrailerWeight(); }); // Update default max tongue weight if payload or percentage changes payloadCapacityInput.addEventListener('input', function() { var payload = parseFloat(payloadCapacityInput.value); var percentage = parseFloat(tongueWeightPercentageInput.value) / 100; if (!isNaN(payload) && !isNaN(percentage) && percentage > 0) { var defaultMaxTongueWeight = Math.round(payload * percentage); // Only update if the input field is empty or if the default calculation is significantly different if (maxTongueWeightInput.value === " || Math.abs(parseFloat(maxTongueWeightInput.value) – defaultMaxTongueWeight) > 10) { // maxTongueWeightInput.value = defaultMaxTongueWeight; // Optional: auto-set max tongue weight } } }); tongueWeightPercentageInput.addEventListener('change', function() { var payload = parseFloat(payloadCapacityInput.value); var percentage = parseFloat(tongueWeightPercentageInput.value) / 100; if (!isNaN(payload) && !isNaN(percentage) && percentage > 0) { var defaultMaxTongueWeight = Math.round(payload * percentage); if (maxTongueWeightInput.value === " || Math.abs(parseFloat(maxTongueWeightInput.value) – defaultMaxTongueWeight) > 10) { // maxTongueWeightInput.value = defaultMaxTongueWeight; // Optional: auto-set max tongue weight } } }); // Re-validate when inputs change vehicleCurbWeightInput.addEventListener('input', calculateMaxTrailerWeight); payloadCapacityInput.addEventListener('input', calculateMaxTrailerWeight); tongueWeightPercentageInput.addEventListener('change', calculateMaxTrailerWeight); maxTongueWeightInput.addEventListener('input', calculateMaxTrailerWeight);

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