Gross weight is the number on the rate con, but scales write tickets per axle. A van at 78,000 lb can still be overweight on the drives, and a short wheelbase can fail the bridge formula with everything else legal. This axle weight calculator checks all of it from your scale ticket.
How it is calculated
Every check compares a weight to a federal Interstate limit:
| Check | Weight | Limit |
|---|---|---|
| Steer axle | steer | the limit you set (federal single axle is 20,000 lb) |
| Drive tandem | drives | 34,000 lb |
| Trailer tandem | trailer | 34,000 lb |
| Gross | steer + drives + trailer | 80,000 lb |
| Outer bridge | gross | bridge formula, 5 axles, steer to last trailer axle |
| Inner bridge | drives + trailer | bridge formula, 4 axles, first drive to last trailer axle |
The bridge formula is W = 500 × (L × N ÷ (N − 1) + 12N + 36), where L is the distance in feet between the outer axles of the group and N is the number of axles, rounded to the nearest 500 lb as the federal table does. Two tandems at least 36 feet apart may carry 34,000 lb each.
A worked example
- Steer 11,500 lb, limit 12,000
- 500 spare
- Drives 35,200 lb, limit 34,000
- 1,200 over
- Trailer 32,800 lb, limit 34,000
- 1,200 spare
- Gross 79,500 lb, limit 80,000
- 500 spare
Gross is legal; the drives aren't. Sliding the trailer tandems toward the nose moves weight off the drives and onto the trailer axles, which have 1,200 lb of room here. How much each hole moves is in the tandem slide calculator.
Truck axle weight tips
- Weigh on a certified scale after loading, not after you're a hundred miles out.
- Power only drivers can't pick how a preloaded trailer was loaded. If it scales heavy on an axle, call before you leave the yard; moving the tandems may fix it.
- Spread axle trailers carry weight differently; see spread axle trailer.
- How much freight a 53 ft van can legally carry depends on your tractor's weight: max weight for a 53 ft dry van.
Multi-stop loads change weight at every stop, so check the heaviest leg; the multi-stop load pay calculator helps price those. Pulling preloaded trailers is covered in power only dispatch.
These are federal Interstate limits. State roads, permits and grandfathered rules can differ, so check the states on your route.
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