Axle Weight Distribution Calculator inputs are the wheelbase, empty axle weights and where each load sits, and the output is each axle load checked against the door jamb’s ratings.
Enter each load’s weight and its distance behind the front axle center, measured to the middle of the load. Use a negative distance for anything ahead of the front axle.
| Load | Weight | Lever | Front Axle | Rear Axle |
|---|---|---|---|---|
| Vehicle, empty | 5,200 lb | 0.42× | 3,000 lb | 2,200 lb |
| Driver | 180 lb | 0.41× | +106 lb | +74 lb |
| Cargo at the tailgate | 1,500 lb | 1.23× | −341 lb | +1,841 lb |
| On the scale | 6,880 lb | 0.60× | 2,764 lb | 4,116 lb |
What the Axle Weight Distribution Calculator Shows
The Axle Weight Distribution Calculator works out how much of a loaded vehicle’s weight sits on the front axle and how much on the rear. It then checks each axle against its rating and the total against the GVWR.
Pickup owners hauling cargo, RV owners checking tongue weight, and installers adding a plow or service body use it before a trip to the scale. It shows which rating runs out first and how far to move a load to fix it.
Vehicle Ratings and Load Rows
Start with a vehicle type preset, then replace every number with your own. The presets are rough starting values. GAWR and GVWR are defined in 49 CFR 571.3, and your door jamb label lists the real figures for your truck.
Empty axle weights come from a scale ticket, with fuel and permanent accessories on board. The US setting uses pounds and inches, and the metric setting uses kilograms and millimeters (1 lb = 0.45359 kg, 1 in = 25.4 mm).
Each load row takes a weight and a distance behind the front axle, measured to the middle of the load. Anything ahead of the front axle, such as a plow or winch, gets a negative distance. The tool holds up to eight loads, plus a separate trailer tongue weight and the hitch ball distance behind the rear axle.
The Lever Behind Every Axle Split
Truck body builders use the same moment balance to place bodies and equipment on a chassis, as Trailer/Body Builders magazine and TruckScience both lay out. Take moments about the front axle, and each load’s rear share follows.
$$R = \frac{W \times x}{L}$$
Here W is the load, x is its distance behind the front axle, and L is the wheelbase. The front axle gets the rest, so the front share is W minus R.
The ratio x ÷ L is the lever shown in the load table. Measure x from the front axle, not the rear. Body specs often quote the center of gravity from the rear axle, and entering that number puts the load far too close to the cab.
A trailer tongue uses the same formula with x set to the wheelbase plus the hitch distance. The Axle Weight Distribution Calculator adds that row for you whenever the tongue weight is above zero.
Loads Behind the Rear Axle
Once a load sits past the rear axle, the lever goes above 1.0. The rear axle then gains more than the load weighs, and the front axle loses weight.
The default shows it clearly. 1,500 lb against the tailgate at 178 in on a 145 in wheelbase has a lever of 1.23, so it adds 1,841 lb to the rear axle and takes 341 lb off the front.
Hitch weight works the same way. An iRV2 forum member worked his own truck through it, with a 140 in wheelbase and the ball 57 in behind the axle. A 600 lb tongue added about 844 lb to his rear axle, while a fifth wheel pin 15 in behind the axle would add only about 664 lb.
Loads Ahead of the Front Axle
A negative distance flips the effect. A snowplow hanging ahead of the bumper adds more than its own weight to the front axle and lifts weight off the rear.
Plow makers deal with this using ballast. Fisher and Western installation guides require ballast secured behind the rear wheels and cap it at 1,000 lb. Meyer asks for ballast at least 24 in behind the rear axle.
Enter the ballast as its own load in the Axle Weight Distribution Calculator to see the result. 400 lb placed 24 in behind the rear axle on a 145 in wheelbase takes about 66 lb off the front axle.
Reading the Axle Weight Distribution Calculator Results
The hero figure is the loaded front and rear split as a percentage, with the total scale weight below it. At the defaults that is 40.2% front and 59.8% rear on 6,880 lb.
Front and Rear Axle Cards
The first two cards show each axle’s load, the share of its GAWR used, and the change from empty. At the defaults the front carries 2,764 lb, 236 lb lighter than empty, while the rear carries 4,116 lb, or 100.4% of its rating.
GAWR is a static rating. An NHTSA interpretation explains it is checked with the vehicle at rest, which is exactly how this calculator and a scale measure it.
GVWR Card and the First Limit Hit
The third card shows GVWR used, the room left, and which of the three ratings runs out first. At the defaults the truck is at 98.3% of GVWR with 120 lb to spare, yet the rear axle is already over.
That gap is common. Alaskan Campers warns truck camper owners that a truck can pass on GVWR and still exceed the rear GAWR. The two axle ratings usually add up to more than the GVWR, but you can never use both in full at once.
Loaded Balance Point
The fourth card gives the loaded center of gravity, measured behind the front axle. The defaults move it from 61.3 in empty to 86.7 in loaded, a 25.4 in shift toward the rear.
The same card shows the empty front share, 57.7% here, so you can see how far the load moved the balance. For service and dump bodies, Trailer/Body Builders gives a rule of thumb of about 60 to 70 percent of the body ahead of the rear axle centerline.
Load Table and Fix Suggestions
The table lists what each load does to each axle, with any axle over its rating shown in red. It is the fastest way to find which load is causing the problem.
When one axle is over and the gross is legal, the alert suggests a move instead of unloading. At the defaults, sliding the tailgate cargo about 2 in forward clears the rear axle, because each inch forward moves about 10 lb off it.
If the front axle ends up lighter than empty, the alert points to a weight distribution hitch. Vehicle and hitch makers now call for restoring 50 to 100 percent of the load the tongue took off the front axle, and SAE J2807 testing advises staying at or under 100 percent.
Where the Axle Weight Distribution Calculator Stops
Wheelbase, empty axle weights, and all three ratings must be above zero. Load weights, tongue weight, and hitch distance cannot be negative, though load distances can be.
If loads sit so far back or forward that one axle would carry nothing, the tool stops and says which wheels would lift. That is the point where the two-support beam model no longer describes a real vehicle.
The math is static and assumes two axles on level ground. It does not cover tandem or tri-axle trucks, left-to-right imbalance, or the extra moment from weight distribution bars and air springs. Real axle loads also change with braking, bumps, and grades, so confirm the plan on a certified scale.
Weighing Mistakes That Skew the Split
Adding the tongue weight on top of a hitched scale ticket counts it twice. Alaskan Campers points out that once the trailer is connected, the tongue load is already inside the truck’s axle weights.
Measuring to the front edge of a load instead of its middle understates the rear share. A pallet that is 40 in long is off by 20 in, which at 1,500 lb is about 207 lb on a 145 in wheelbase.
Weighing the empty truck on a low tank also hides load that returns at the pump. The Fuel Weight Calculator shows how much a full tank adds, so weigh full or enter the missing fuel as a load.
Axle Load Questions From Truck Owners
How do you calculate front and rear axle weight?
Multiply each load by its distance behind the front axle, then divide by the wheelbase to get its rear share. The front axle takes the rest. Add those shares to the empty axle weights, which is what the Axle Weight Distribution Calculator does for every row. With the defaults, a 5,200 lb truck plus a 180 lb driver and 1,500 lb of cargo ends up with 2,764 lb front and 4,116 lb rear.
Can you be under GVWR but over the rear GAWR?
Yes, and it happens often with bed loads, campers, and trailers. The default example is 120 lb under GVWR while 16 lb over the rear GAWR. Both limits apply at once, so an axle over its rating is overloaded no matter what the gross says.
How much weight does a trailer tongue put on the rear axle?
More than the tongue weight itself, because the ball sits behind the axle. A 700 lb tongue 50 in behind the rear axle of a 145 in wheelbase truck adds about 941 lb to the rear and removes about 241 lb from the front.
How do you find tongue weight at a CAT scale?
Towing forum members use two weighings. Weigh the loaded truck alone, then weigh it again hitched with the weight distribution bars off. The increase in the truck’s total is the tongue weight. Enter that figure in the Axle Weight Distribution Calculator’s tongue field, not on top of the hitched axle weights.
Where should heavy cargo go in a pickup bed?
As far forward as it can safely sit, against the bulkhead and ahead of the rear axle when possible. Every inch forward takes the load’s weight divided by the wheelbase off the rear axle. For 1,500 lb on a 145 in wheelbase, that is about 10 lb per inch. Moving it 15 in toward the cab frees about 155 lb of rear axle capacity without removing anything.