Wisconsin truck weight limits
On Interstate highways in Wisconsin, federal weight limits apply. Four checks decide whether your truck is legal — and the one that surprises most drivers is the Federal Bridge Formula, which can fail a truck that passes every other limit.
Federal limits on Wisconsin Interstates
| Limit | Maximum | Applies to |
|---|---|---|
| Single axle | 20,000 lb | Any one axle |
| Tandem axle group | 34,000 lb | Axles 40–96 inches apart |
| Tridem axle group | governed by the bridge formula | 3 axles in a group (no flat federal cap) |
| Gross vehicle weight | 80,000 lb | The whole rig |
| Bridge formula | varies by spacing | Every group of 2+ axles |
The bridge formula check
L is the spacing in feet between the outer axles of a group, N the number of axles. A standard 5-axle rig at 51 ft is capped at 79,500 lb by this formula — under the 80,000 lb gross limit. Full explanation with worked examples.
Wisconsin-specific rules
Wisconsin splits its highways into Class "A" and Class "B", and knowing which you're on is the whole game off the Interstate. On the Interstate and on Class A highways the limits are the standard 20,000 lb single axle, 34,000 lb tandem, 80,000 lb gross, plus an 11,000 lb per wheel-end limit and the Federal Bridge Formula (Wis. Stat. § 348.15). Class B highways carry sharply reduced limits (posted, roughly 60% of Class A). Wisconsin also grants agriculture generous room — a 23,000 lb single axle for implements of husbandry and a 15% seasonal harvest allowance on certain crops.
Wisconsin exceptions to the federal limits
Wisconsin limits by highway class (Wis. Stat. § 348.15):
| Measure | Class "A" highways | Class "B" highways |
|---|---|---|
| Single axle | 20,000 lb (23,000 lb for ag) | reduced (posted) |
| Tandem axle group | 34,000 lb | reduced (posted) |
| Per wheel-end | 11,000 lb | reduced |
| Maximum gross | 80,000 lb | reduced (posted) |
- Two consecutive tandem sets may each carry 34,000 lb where the extreme axles are 36 ft or more apart.
- Agricultural harvest allowance: from Aug 1 – Dec 31, no permit is required to move corn, soybeans, potatoes, vegetables or cranberries from the field that exceed the § 348.15 limits by up to 15%.
- On Interstates, federal limits govern — 20,000 / 34,000 / 80,000 plus the bridge formula.
Seasonal & designated-route rules in Wisconsin
Two seasonal layers matter in Wisconsin. Spring thaw postings: during the thaw, WisDOT and local authorities post reduced weight limits on frost-susceptible routes — check current postings before running heavy in spring. Agricultural harvest window: from August 1 to December 31, listed crops moving from the field get up to a 15% overweight allowance without a permit. Class B highway limits also apply year-round on posted routes and are much lower than Class A.
Overweight permits in Wisconsin
Loads over the legal limits — or over a Class B posting — need an oversize/overweight permit from WisDOT (single-trip or annual), route-specific by bridge and pavement rating.
Fines & enforcement in Wisconsin
Enforced by the Wisconsin State Patrol at fixed scales and with portable/mobile enforcement. Overweight violations carry graduated per-pound penalties; loads can be held until brought within limits.
What dispatchers should check in Wisconsin
- Class A vs. Class B — a Class B posting can cut your legal weight by roughly 40%; confirm the class of every non-Interstate road on the route.
- Agricultural moves — the 23,000 lb ag single axle and the 15% Aug–Dec harvest allowance apply only to qualifying loads.
- Spring thaw — check WisDOT and local postings before running heavy in spring.
- Interstate — federal 20,000 / 34,000 / 80,000 plus the bridge formula.
Wisconsin truck weight — frequently asked questions
How much can a truck weigh in Wisconsin?
On Wisconsin Interstates the federal gross-weight limit is 80,000 lb, with a 20,000 lb single-axle limit, a 34,000 lb tandem limit and the Federal Bridge Formula. Wisconsin sets its own limits on non-Interstate roads — see the Wisconsin-specific rules on this page.
Does Wisconsin follow federal truck weight limits?
On the Interstate system, yes — federal limits govern in every state. Off the Interstate, Wisconsin applies its own axle, gross and permit rules, detailed on this page where they have been verified against the official state source.
What is the single-axle weight limit in Wisconsin?
The federal single-axle limit of 20,000 lb applies on Wisconsin Interstates. Some states set a different single-axle figure on non-Interstate roads — check the Wisconsin-specific section above for the governing number.
What is the maximum tandem-axle weight in Wisconsin?
On Wisconsin Interstates the federal tandem limit is 34,000 lb. Several states allow a different tandem weight on non-Interstate roads — see the Wisconsin exceptions above for the figure that governs.
Scaled heavy in Wisconsin?
If the trailer tandems are over, the fix is usually a computed tandem slide, not unloading — see how sliding tandems shifts weight. And here's what an overweight ticket really costs before you decide to run it.
Run your scale-ticket weights through the federal and bridge-formula calculator in your browser. The full platform predicts axle loads from load placement before you load, computes the exact slide-to-legal fix, and applies Wisconsin rules on top of the federal baseline.
Open the free calculatorOur calculator runs the federal single, tandem, gross and Bridge Formula checks in seconds. The full platform adds per-state limits, axle-load prediction and the slide-to-legal fix.
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