Pennsylvania truck weight limits
On Interstate highways in Pennsylvania, 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 Pennsylvania 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.
Pennsylvania-specific rules
- Limits under Title 75 Ch. 49 match federal: 20,000 lb single axle, 34,000 lb tandem, 80,000 lb gross (single vehicle or combination).
- Combinations registered above 73,280 lb carry extra axle-spacing conditions — two consecutive tandems at 34,000 lb each need at least 36 ft between first and last axles.
- Many local roads and bridges are weight-posted below state limits; permits are issued by PennDOT under Chapter 49.
US-PA and the verdict applies Pennsylvania-specific limits on top of the federal baseline.Pennsylvania truck weight — frequently asked questions
How much can a truck weigh in Pennsylvania?
On Pennsylvania 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. Pennsylvania sets its own limits on non-Interstate roads — see the Pennsylvania-specific rules on this page.
Does Pennsylvania follow federal truck weight limits?
On the Interstate system, yes — federal limits govern in every state. Off the Interstate, Pennsylvania 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 Pennsylvania?
The federal single-axle limit of 20,000 lb applies on Pennsylvania Interstates. Some states set a different single-axle figure on non-Interstate roads — check the Pennsylvania-specific section above for the governing number.
What is the maximum tandem-axle weight in Pennsylvania?
On Pennsylvania Interstates the federal tandem limit is 34,000 lb. Several states allow a different tandem weight on non-Interstate roads — see the Pennsylvania exceptions above for the figure that governs.
Scaled heavy in Pennsylvania?
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 Pennsylvania 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.
Try the free calculator