Axle Weight Calculator

The federal gross vehicle weight limit is 80,000 lbs on Interstate highways. This breaks down to 20,000 lbs on a single axle (steer), 34,000 lbs on a tandem axle group, and the total must also comply with the Federal Bridge Formula. Some states allow higher weights on non-Interstate roads with permits.

The Bridge Formula (also called Formula B) calculates the maximum allowable weight based on the number of axles and the distance between the outermost axles. It prevents excessive weight concentration that could damage bridges. Even if individual axle weights are legal, the bridge formula may further limit your gross weight. The formula is: W = 500 × ((L × N)/(N-1) + 12N + 36).

Michigan has a unique weight law that allows up to 164,000 lbs on 11-axle configurations on state roads (not Interstates). This dates back to Michigan's heavy manufacturing history. The key is axle spacing — Michigan uses a more generous axle weight table rather than the federal bridge formula. Trucks must use special multi-axle trailer configurations to qualify.

Proper weight distribution depends on where you place the cargo in the trailer. Center-loading is safest for most freight. Nose-heavy loads put extra stress on the steer and drive axles, while tail-heavy loads overload trailer axles and reduce steering traction. Use a CAT scale to verify actual axle weights before hitting the highway.

Overweight fines vary significantly by state. Many states charge per-pound fines that increase with the amount over — for example, $0.05 per pound for the first 2,000 lbs over, then $0.10 per pound after that. Some states like California can issue fines up to $16,000+. You may also be placed out of service until weight is reduced, costing you time and money.