How it works
The calculator treats the vehicle as a beam resting on its two axles and takes moments about the rear axle (the lever rule). A load behind the rear axle lifts the front; a load between the axles is shared according to how close it is to each one.
Tongue weight T at overhang OH: front −T × OH ÷ WB, rear +T × (WB + OH) ÷ WB
Cargo C at distance d ahead of the rear axle: front +C × d ÷ WB, rear +C × (WB − d) ÷ WB
Loaded axle = unloaded axle + change
Worked example
Truck with 3,600 lb front and 2,900 lb rear, 145 in wheelbase, 48 in from rear axle to ball, 800 lb tongue weight and 400 lb of cargo 30 in ahead of the rear axle.
- Tongue weight: front −800 × 48 ÷ 145 = −265 lb; rear +1,065 lb.
- Cargo: front +400 × 30 ÷ 145 = +83 lb; rear +317 lb.
- Loaded: front 3,418 lb, rear 4,282 lb, just under a 4,300 lb rear GAWR.
Rear axle gain by hitch overhang
Extra load on the rear axle (and load lifted off the front) for a 145 in wheelbase.
| Rear axle to ball | 500 lb tongue | 800 lb tongue | 1,100 lb tongue |
|---|---|---|---|
| 36 in | +624 / -124 lb | +999 / -199 lb | +1,373 / -273 lb |
| 42 in | +645 / -145 lb | +1,032 / -232 lb | +1,419 / -319 lb |
| 48 in | +666 / -166 lb | +1,065 / -265 lb | +1,464 / -364 lb |
| 54 in | +686 / -186 lb | +1,098 / -298 lb | +1,510 / -410 lb |
| 60 in | +707 / -207 lb | +1,131 / -331 lb | +1,555 / -455 lb |
Getting real axle weights
The most accurate numbers come from a certified truck scale with separate pads for each axle. Weigh the vehicle unhitched with a full tank and the people you usually carry, then hitched. Without a scale, you can split the curb weight roughly 55/45 front to rear for most pickups, but treat the result as an estimate.
If the rear axle is close to its rating, a weight distribution hitch can move part of the load forward and back to the trailer. Also check the total against your availablepayload.
Common mistakes
- Checking only GVWR. A truck can be under GVWR and still over its rear GAWR.
- Ignoring overhang. A long ball mount or bumper hitch adds a lot of rear axle load.
- Loading heavy gear at the tailgate. Weight behind the rear axle acts like extra tongue weight.
- Guessing axle weights. One trip to a scale replaces every guess on this page.