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Trailer Weight Distribution Calculator: Axle Loads, WDH Sizing, and Sway

Most WDH calculators only tell you that you need one. This one tells you exactly how many pounds your front axle loses, how much the rear axle gains, whether those loads exceed your GAWR limits, and how much a properly sized WDH transfers back — in actual numbers you can verify at a truck stop scale.

⚖️ Vehicle, Trailer, and WDH Inputs
📋 Tow Vehicle Ratings
lbs
lbs
lbs
lbs
GAWR and curb weight improve axle load accuracy. All are on the door-jamb sticker or owner’s manual.
🚜 Trailer and Tongue Weight
lbs
Weigh your trailer fully loaded for travel, including water, food, gear, and any cargo.
%
Bumper pull: 10-15% | Gooseneck: 20-30% | Fifth wheel: 15-25%
👥 Truck Cab Load
people
⚖️ WDH (if you have one)
lbs
Printed on the WDH spring bar or head. Common sizes: 600, 800, 1000, 1200, 1400, 1700, 2000 lbs.
📊 Axle Load Analysis
⚖️
Enter your vehicle GVWR, loaded trailer weight, and tongue weight. The calculator shows exact front and rear axle loads before and after WDH, GAWR compliance, and recommended WDH class.

What a Weight Distribution Hitch Actually Does to Your Axle Loads

Every bumper-pull trailer that weighs more than about 5,000 lbs puts your truck’s front axle in a compromising position, and understanding exactly why requires thinking about the physics of a hitch ball mounted behind the rear axle of your truck.

When you attach a loaded trailer to a ball mount, the tongue weight pushes down at the hitch point. That hitch point is typically 24 to 36 inches behind the rear axle of a full-size pickup truck. Because it is behind the rear axle, the tongue weight creates a leveraging effect: the rear of the truck is pushed down, and the front of the truck is lifted up. This is not a small number. For a truck with a typical wheelbase of 144 to 157 inches and a hitch ball approximately 30 inches behind the rear axle, the physics works out to roughly 20 percent of the tongue weight being removed from the front axle. A 1,000-lb tongue weight removes approximately 200 lbs from your front axle. That is 200 lbs of steering and braking force that your front tires are no longer pressing into the pavement.

The Front Axle Calculation Most Calculators Skip Entirely

The 200-lb front lift sounds manageable in isolation. But consider what it means in the context of your truck. A half-ton pickup typically has 3,200 to 3,600 lbs on the front axle when loaded with passengers and fuel. Losing 200 lbs is a 5 to 6 percent reduction. That is a measurable change in steering response and braking distance. Now consider a heavier scenario: a 1,400-lb tongue weight removes 280 lbs from the front axle. On a lighter SUV with 2,400 lbs on the front axle, that is an 11 percent reduction. Braking distance increases. Steering feel becomes numb. The handling characteristics of the whole rig change in ways that catch inexperienced towers off guard at highway speeds.

The National Highway Traffic Safety Administration recommends that towers use a WDH when tongue weight exceeds 10 percent of the tow vehicle GVWR. This calculator shows you the exact number your front axle is working with, not just whether you are above or below a threshold.

The Rear Axle Gets More Than Just Tongue Weight

While the front axle loses weight, the rear axle gains considerably more than just the tongue weight itself. Because the tongue weight acts behind the rear axle, the rear axle must support both the tongue weight and absorb the cantilever reaction that would otherwise lift the front. For the same 30-inch overhang on a 150-inch wheelbase, the rear axle gains approximately 120 percent of the tongue weight, not just 100 percent. A 1,000-lb tongue weight adds roughly 1,200 lbs to your rear axle. This is why heavy tongue weights can exceed the Rear Gross Axle Weight Rating (GAWR-R) printed on your door jamb sticker long before you hit the overall GVWR limit.

What WDH Does and Does Not Fix

A properly sized and adjusted weight distribution hitch applies spring bar torque that lifts the rear of the truck slightly and depresses the tongue of the trailer slightly. This transfers a portion of the tongue weight back from the rear axle toward the front axle and the trailer axles. A properly set WDH at its rated tongue weight typically transfers approximately 50 percent of the tongue weight. For a 1,000-lb tongue weight, that means about 500 lbs transferred: roughly 410 lbs back to the front axle and 90 lbs to the trailer axles (the exact split depends on trailer type and suspension design).

What a WDH does not do: it does not reduce your total tongue weight, it does not change your overall GCWR or towing capacity rating, and it does not replace a sway control system. A WDH and sway control serve different purposes. The WDH redistributes vertical weight. Sway control (either friction-type or electronic, like Trailer Sway Control built into many modern trucks) manages lateral forces and yaw motion. Many integrated systems like the Equal-i-zer and B&W Continuum combine both functions.

How the Axle Load Calculator Works: Inputs, Physics, and Outputs

This calculator uses a physics-based model of a two-axle tow vehicle to estimate front and rear axle loads before and after WDH engagement. The inputs required and how each affects the result are explained below.

Vehicle Ratings: GVWR, GAWR Front, GAWR Rear, and Curb Weight

GVWR is the gross vehicle weight rating: the maximum legal weight of your loaded truck including all passengers, cargo, and fuel. It drives the WDH need assessment. GAWR-F (front gross axle weight rating) and GAWR-R (rear gross axle weight rating) are the maximum individual axle load ratings. All three are on the yellow sticker inside the driver-side door jamb. Curb weight, available in the owner’s manual or by VIN lookup, lets the calculator estimate actual front and rear base loads. If you skip curb weight, the calculator uses a reasonable estimate based on GVWR.

Tongue Weight: Estimate or Measured Value

You can enter tongue weight two ways. The estimate method multiplies your loaded GTW by a percentage you specify, defaulting to 12 percent (the middle of the 10-15 percent conventional bumper-pull range). If you have weighed your tongue weight with a tongue weight scale or at a CAT Scale using the before/after rear axle weight method, enter the measured lbs directly. The measured approach is more accurate and is what this calculator uses when you enter a real number. If your tongue weight percentage is outside the typical range for your trailer type, review your cargo placement before towing.

WDH Spring Bar Rating: How Transfer Amount Is Calculated

The WDH spring bar rating is the maximum tongue weight the system is designed to handle at full engagement. When entered, the calculator estimates the transfer amount: approximately 50 percent of tongue weight for a WDH rated at or above your tongue weight, declining to 34 percent for a significantly under-rated WDH. The split of transferred weight is approximately 82 percent to the front axle and 18 percent to the trailer axles, based on standard industry observations. Your actual results will vary based on WDH type, head angle adjustment, and trailer geometry.

Three Real US Weight Distribution Scenarios with Complete Axle Load Numbers

Setup 1 Near Austin, TX: Ford Explorer Towing a Pop-Up Camper

Jessica and her family tow a 4,200-lb loaded pop-up camper on weekends outside Austin. Her 2023 Ford Explorer has a 6,500-lb GVWR, a 3,900-lb GAWR-R, and a 3,000-lb curb weight loaded. She tows with two adults and two kids in the Explorer. Her tongue weight at 12 percent is 504 lbs.

ConditionFront AxleRear AxleAssessment
Unhitched (loaded truck)1,896 lbs1,752 lbsNormal
Hitched, no WDH1,796 lbs2,357 lbs-100 lbs front / +605 lbs rear
Rear GAWR-R check2,357 vs 3,900 lbs GAWR-RWithin GAWR-R (safe)
WDH Needed?Tongue weight: 7.8% of GVWRNo WDH required (under 10%)

At 7.8 percent of GVWR and 504 lbs absolute, a WDH is technically not required. Jessica’s rear axle stays well within its 3,900-lb rating. The 100-lb front lift is minor and within normal operating margins. However, as the kids grow and she adds more camping gear, her tongue weight will grow. At 640 lbs (10 percent of GVWR), a WDH becomes recommended. This is the scenario where knowing your exact numbers prevents a premature purchase.

Setup 2 in Colorado: Ram 1500 Towing a 28-ft Travel Trailer at Altitude

Marcus and his wife are full-timing in a 2022 Ram 1500 Hemi towing their 28-foot travel trailer between Colorado campgrounds. The Ram has a 7,100-lb GVWR, a 4,100-lb GAWR-R, and weighs 5,200 lbs loaded with full water tank and two adults. Their trailer weighs 8,800 lbs loaded and the tongue weight is 1,056 lbs at 12 percent.

ConditionFront AxleRear AxleAssessment
Unhitched (loaded truck)2,808 lbs2,597 lbsNormal
Hitched, no WDH2,597 lbs3,864 lbs-211 lbs front / +1,267 lbs rear
Rear GAWR-R check3,864 vs 4,100 lbs GAWR-RWithin GAWR-R but only 236 lbs margin
With 1,000 lb WDH2,832 lbs (+235)3,336 lbs (-528)Rear: 764 lbs margin from GAWR-R
WDH Needed?TW: 14.9% of GVWR, 1,056 lbsStrongly recommended

Marcus’s setup needs a WDH badly. At 14.9 percent of GVWR, his tongue weight is nearly 50 percent above the 10 percent threshold. Without a WDH, he has only 236 lbs of margin before he exceeds his GAWR-R. At Colorado mountain passes where the altitude saps engine power, managing trailer sway becomes critical. A 1,000-lb WDH properly set restores 235 lbs to the front axle and creates a comfortable 764-lb safety margin on the rear. He should choose a WDH with integrated sway control, such as the Equal-i-zer 10K or the B&W Continuum, given his mountain towing conditions.

Setup 3 in Tennessee: Ford F-250 Towing a Cargo Trailer on I-40

Donna runs a small landscaping business in Nashville and tows a 12,000-lb enclosed cargo trailer on an F-250 XL with a 10,000-lb GVWR and 6,400-lb GAWR-R. Her loaded truck with one employee weighs 7,200 lbs. Tongue weight at 12 percent is 1,440 lbs.

ConditionFront AxleRear AxleAssessment
Unhitched (loaded truck)3,878 lbs3,583 lbsNormal
Hitched, no WDH3,590 lbs5,310 lbs-288 lbs front / +1,727 lbs rear
Rear GAWR-R check5,310 vs 6,400 lbs GAWR-R1,090 lbs margin (still within, but tight)
With 1,400 lb WDH3,877 lbs (+287)4,590 lbs (-720)Rear: 1,810 lbs margin from GAWR-R
WDH Needed?TW: 14.4% of GVWR, 1,440 lbsStrongly recommended

Donna’s cargo trailer setup shows why even a three-quarter-ton truck benefits from a WDH. Without it, her rear axle carries 5,310 lbs while her front drops 288 lbs. A 1,400-lb WDH rated for her tongue weight nearly fully restores the front axle to its unloaded weight and creates a comfortable 1,810-lb rear axle safety margin. For a commercial landscaping truck on interstate highways, proper weight distribution is also a DOT compliance issue; a commercial driver stopped at a weigh station with axle weights exceeding GAWR can face fines and out-of-service orders.

Three Expert Tips for Correctly Setting Your Weight Distribution Hitch

Tip 1: Use the Tape Measure Front Axle Method to Verify Your WDH Setup

The most reliable way to verify that your WDH is properly transferring weight is the front axle height method, sometimes called the tape measure test. Before you hitch any trailer, measure the distance from the ground to the top of the wheel arch or to a consistent reference point on the front fender of your unloaded truck. Write that number down. Now hitch the trailer without engaging the spring bars. Measure again. The front should rise slightly (front lifts when tongue weight is applied). Now engage and adjust the WDH spring bars until the front of the truck returns to as close to the original pre-hitchup measurement as possible. When the front is back to its original height, the WDH is working correctly. If you cannot get it back to the original height, your WDH is under-rated for your tongue weight and you should move up to the next size class.

Tip 2: Size Your WDH for the Middle of Its Rated Range, Not the Maximum

Every WDH has a rated tongue weight range, not just a maximum. A 1,000-lb WDH might be rated for 600 to 1,000 lbs. If your tongue weight is 990 lbs, you are at the top of the range with no adjustment margin remaining. The industry recommendation from manufacturers and towing safety experts is to select a WDH where your tongue weight falls in the middle third of the rated range. If your tongue weight is 900 lbs, a 1,000-lb WDH (range 600-1,000) is too close to maximum. A 1,200-lb WDH (range 800-1,200) puts you comfortably in the middle. This also gives you margin when you pick up extra cargo on the trailer unexpectedly, which pushes tongue weight up before you have a chance to reweigh.

Tip 3: Weigh Your Setup at a CAT Scale Before Every Season Change

CAT Scales, found at most major US truck stop locations including Pilot Flying J and Love’s Travel Stops, provide a printed ticket with individual axle weights for approximately $12 to $15. For a weight distribution verification, weigh your setup twice: once with the WDH spring bars disengaged and once with them engaged. The difference in rear axle weight between the two readings is the actual WDH transfer amount. Compare this to the manufacturer’s published transfer rate for your WDH and your tongue weight. If the actual transfer is significantly below the expected range, your head angle is too shallow and needs adjustment. This simple field test is the most reliable confirmation that your WDH is set correctly, and no calculator can replace real scale weights.

16 Weight Distribution Hitch Questions Answered for US Towers

A properly sized and adjusted weight distribution hitch transfers approximately 50 percent of the trailer tongue weight back from the rear axle toward the front axle and trailer axles. Of that transferred weight, roughly 80 to 85 percent goes to the front axle and 15 to 20 percent goes to the trailer axles. The exact percentage depends on the WDH design type, the head angle adjustment, the trailer suspension type, and how accurately the WDH is rated to match the actual tongue weight. An under-rated WDH (rated below actual tongue weight) transfers a lower percentage, often only 34 to 40 percent, which is why proper WDH sizing matters.
There is no single federal law requiring a WDH at a specific tongue weight. The requirement typically comes from the vehicle manufacturer. Most truck and SUV manufacturers state in their towing guides that a WDH is required when tongue weight exceeds 10 percent of the tow vehicle’s loaded weight (GVWR) or when the trailer weight exceeds a certain threshold. Some manufacturers also specify that towing with tongue weight above 350 to 400 lbs without a WDH voids certain warranties. The NHTSA recommends WDH use when tongue weight exceeds 10 percent of tow vehicle GVWR. Check your specific owner’s manual and towing guide for the exact requirement that applies to your truck or SUV.
A weight distribution hitch addresses vertical weight transfer: it redistributes the tongue weight from the rear axle back to the front axle to restore steering and braking response. A sway control device addresses lateral movement: it damps side-to-side oscillation of the trailer to prevent trailer sway from becoming trailer whip. These are two different problems requiring different solutions. A WDH does not prevent sway. Sway control does not fix the front-axle weight loss from tongue weight. Most serious towers use both. Integrated systems like the Equal-i-zer 4-point and the B&W Continuum combine both functions in one head assembly, which simplifies hookup and ensures both issues are addressed simultaneously.
No. Fifth-wheel trailers connect to a hitch head plate positioned over or ahead of the rear axle in the truck bed, not behind it like a ball hitch. The physics of a connection point over the rear axle means the tongue weight (pin weight) does not create the same leveraging effect that lifts the front of the truck. Fifth-wheel connection actually adds weight slightly toward the front compared to a bumper-pull trailer with equivalent tongue weight. As a result, fifth-wheel setups do not require and cannot effectively use a traditional spring-bar weight distribution hitch. Similarly, gooseneck trailers connected through a ball in the truck bed over the rear axle do not typically use or require WDH.
The most accessible method without specialized equipment is the CAT Scale method: weigh your truck alone at a truck stop scale, then weigh your loaded truck with the trailer hitched (no spring bars engaged). The difference in rear axle weight between the two readings approximates your tongue weight, with a small correction factor. For a direct measurement, a tongue weight scale (available for $50 to $150) sits under the trailer coupler when the trailer is level and measures the downward force. A bathroom scale with a block of wood can work for lighter tongue weights under 300 lbs, though accuracy decreases above that threshold. The most accurate method is a certified weigh station or a Sherline-type scale under the coupler.
For a 10,000-lb trailer with 12 percent tongue weight, your tongue weight is 1,200 lbs. At 15 percent (heavier front-loaded cargo), it is 1,500 lbs. A WDH rated at the tongue weight or slightly above is the baseline requirement. For 1,200 lbs, a 1,400-lb WDH is appropriate (tongue weight at the middle of the range). For 1,500 lbs, a 1,700-lb WDH is the correct next step. Popular options at this size include the Reese Strait-Line 1,400, the Equal-i-zer 14K, the B&W 1,400, and the Hensley Arrow. For a 10,000-lb trailer with typical 12 percent tongue weight, sizing up to a 1,400-lb WDH gives you margin for heavier-loaded trips and ensures the spring bars can fully engage at the correct head angle.
The truck’s published towing rating and the WDH requirement are separate questions. A truck rated to tow 12,000 lbs may still require a WDH when tongue weight exceeds 10 percent of GVWR, per the manufacturer’s towing guide. You can technically drive without a WDH even when one is recommended, but doing so can: reduce front axle traction and braking effectiveness, increase stopping distance, make steering feel numb or vague, increase the risk of trailer sway, and in some cases void warranty coverage on trailer hitch, suspension, and related components. For trailers over 6,000 lbs or tongue weights over 750 lbs, the practical and safety argument for a WDH is very strong regardless of what the rating technically allows.
The front axle height test (also called the tape measure test) is a simple field method for confirming that your WDH is correctly transferring weight. Before hitching, measure from the ground to a fixed reference point on the front of your unloaded truck, such as the top of the wheel arch. After hitching with spring bars disengaged, the front of the truck should rise (lift) due to the tongue weight cantilever. The amount of lift varies by truck, tongue weight, and wheelbase, but 1 to 3 inches is common for heavy tongue weights. Engage and adjust the spring bars until the front of the truck returns to as close as possible to the original pre-hitchup measurement. When the front axle height matches the original measurement, the WDH has transferred enough weight. This confirms actual weight transfer without a scale.
Trailer sway is a side-to-side oscillation that begins at the trailer and can grow into a dangerous whipping motion if not corrected quickly. The most common causes are: insufficient tongue weight (less than 10 percent of GTW allows the trailer to swing too freely), excessive speed, crosswinds, passing trucks creating air disturbance, improperly balanced cargo (too much weight behind the trailer axle), worn trailer hitch ball, or tires. Low front-axle weight from an overloaded tongue weight without WDH also contributes because the steering wheels have less ground contact. A WDH improves the situation by restoring front axle weight, but if sway control is needed (friction-type or integrated) it should be added as a separate measure. Modern trucks with Trailer Sway Control (electronic, brake-based) provide a last-resort intervention when sway begins.
For towers regularly pulling trailers over 8,000 lbs, yes. Integrated systems like the Equal-i-zer 4-point sway control and the B&W Continuum handle both weight distribution and sway control in a single head assembly. They eliminate the need for a separate friction sway bar or a standalone electronic system. The Equal-i-zer, for example, uses four-point force distribution to simultaneously resist both tongue weight droop and lateral sway, without the need to remove sway bars when backing. The B&W Continuum adds hydraulic damping for an exceptionally smooth ride quality. These systems cost $600 to $1,600 compared to $200 to $400 for a basic spring-bar WDH with a separate friction sway bar, but they deliver meaningfully better real-world handling for serious full-time or frequent towers.
Re-check the front axle height measurement every time you significantly change your trailer load configuration. If you carry less water, more gear, or fewer passengers than usual, your tongue weight changes, and the spring bar setting that was correct for your previous configuration may be too tight or too loose. Also check after any ball mount height change (if you add a truck leveling kit or swap ball mounts), and at the beginning of each towing season. Annual inspection of the WDH hardware for wear, especially the ball and coupler, snap-up bracket pins, and spring bar chains, is also recommended. Some WDH manufacturers recommend greasing the ball socket every 2,000 to 3,000 miles of towing.
Yes. An over-rated WDH (spring bars rated significantly above your tongue weight) may not be able to be properly set to the correct head angle. When head angle is too steep to engage correctly, the spring bars apply uneven force, can cause the trailer coupler to bind, may pop the snap-up brackets loose unexpectedly on bumps, or can stress the truck frame and trailer A-frame. The maximum benefit transfer rate of 50 to 60 percent is achievable only when the WDH is properly matched to the tongue weight. A WDH rated at twice your tongue weight cannot be set to transfer the correct amount of weight and should be replaced with a properly sized unit.
The Andersen No-Sway Weight Distribution Hitch uses round ball sockets and a pivot mechanism instead of the chain-and-bracket system used by traditional spring bar WDHs. The design allows the coupler to swivel freely during backing, eliminating the need to remove sway bars before reversing (a common annoyance with traditional WDHs). The Andersen is also significantly lighter and easier to set up than chain-style WDHs. It is best suited for lighter trailers with tongue weights under approximately 1,000 to 1,200 lbs. For heavier tongue weights and aggressive sway control, traditional round bar or trunnion bar systems like the Equal-i-zer or B&W Continuum provide more force transfer capability.
Yes. The receiver hitch installed on your truck has both a maximum tongue weight rating and a maximum WDH tongue weight rating, which are often different numbers. A Class III receiver rated at 750 lbs tongue weight (without WDH) may be rated at 1,200 lbs tongue weight when used with a WDH, because the WDH distributes the load more evenly through the receiver. These two ratings are stamped on the receiver housing or on the bolt-on label. Your WDH head must fit in the receiver opening (2-inch for most Class III/IV, 2.5-inch for some Class V), and the WDH tongue weight must not exceed the receiver’s WDH-specific rating. Never exceed the receiver hitch’s stated maximum ratings regardless of how your truck’s frame rating may differ.
Yes, but with a caution. Air bag suspension systems (like AirLift or Roadmaster) that add air to the rear leaf or coil spring packs can level the truck after tongue weight causes squat. However, air bags are not a substitute for a WDH. They prevent rear squat but do not transfer weight back to the front axle, which is the core function of a WDH. A truck with air bags but no WDH will sit level but still have a compromised front axle with reduced steering and braking weight. For the best outcome, use both: a WDH to transfer weight from rear to front, and air bags to fine-tune ride height and prevent excessive suspension compression. Many experienced towers run both systems together, especially on one-ton trucks towing heavy fifth wheels or goosenecks.
During straight and level towing, the WDH spring bars transfer weight as calculated. During cornering, the weight distribution shifts as lateral acceleration loads the outside wheels. The WDH continues to operate but the actual front-to-rear balance shifts with the cornering forces. Going uphill reduces the effective tongue weight contribution from gravity (the weight shifts toward the trailer axles), so the WDH may slightly over-transfer on steep upgrades. Going downhill increases the effective tongue weight, which can exceed the WDH’s rated capacity briefly on steep descents. These are the reasons why WDH setup should always be verified on a level surface and why conservative speed management on steep grades is important regardless of WDH setup quality.

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Legal Disclaimer and Editorial Transparency

Axle load estimates in this calculator use a simplified physics model based on a standard pickup truck wheelbase of approximately 150 inches and a hitch overhang of approximately 30 inches behind the rear axle. Your actual axle loads will vary based on your specific vehicle geometry, load distribution, curb weight, and WDH type. Always verify actual axle loads at a certified CAT Scale before towing commercially or near GAWR limits.

WDH transfer percentages are estimates based on industry-standard expectations for properly sized and adjusted systems. Actual transfer varies by WDH model, head angle, spring bar engagement depth, and trailer geometry. WDH recommendations reference popular products for informational purposes only. USCalculators.com has no paid relationship with any WDH manufacturer mentioned on this page.

USCalculators.com is not responsible for vehicle damage, accidents, personal injury, or regulatory fines resulting from use of this calculator. Editorial transparency: No WDH brand, trailer manufacturer, or auto company paid to influence the content or calculations on this page.