Truck weight limit checker

How the checker works

The checker looks at a standard five-axle tractor-trailer: one steer axle, a drive tandem and a trailer tandem. It compares your weights with the federal limits for the Interstate System Source: eCFR, 202623 CFR 658.17 WeighteCFR (Office of the Federal Register), 2026. Checked 2026-10-11.Open the source.

1. Single axle. The steer axle can't carry more than 20,000 lb. In practice, tire ratings and state rules often limit it to less.
2. Tandems. Each tandem can carry up to 34,000 lb.
3. Drives and trailer together. These four axles form a group, checked with the Bridge Formula using the distance from the first drive axle to the last trailer axle. When that distance is 36 ft or more, the two tandems may carry 34,000 lb each even if the formula gives less.
4. Gross weight. The total can't exceed 80,000 lb, or the Bridge Formula limit for all five axles if that's lower.

The Bridge Formula is W = 500(LN/(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. The result is rounded to the nearest 500 lb.

Two worked examples

The second rig has the same weight on every axle, but the axles are closer together. That concentrates the load on a bridge, so the formula allows less.

Reading your result

• Legal on every line. You're within federal Interstate limits. Check state limits for any non-Interstate roads on the route.
• One axle group over, gross legal. Usually fixable by sliding the trailer tandems or moving the fifth wheel, then weighing again.
• Gross over. The load is too heavy for this rig. It needs to be reduced, moved on equipment with more axles, or permitted.

A load can also be legal and still be a problem. Heavy loads take longer to stop and climb hills slowly. The truck stopping distance calculator shows how much extra room weight takes, and the dimension fit checker checks that the freight fits the trailer in the first place.

Reading a scale ticket

A truck stop scale has three platforms, one under each axle group. The ticket shows three weights and a total: steer, drives and trailer. Those are exactly the three numbers this checker asks for, so you can type them straight in.

Measure axle spacing once and write it down. You need two distances: from the center of the steer axle to the center of the last trailer axle, and from the center of the first drive axle to the center of the last trailer axle. The second one changes every time you slide the trailer tandems, so measure it at the slider position you use most.

If the ticket shows a group over its limit, adjust and weigh again. Most scales allow a reweigh at a lower price. Sliding the tandems moves weight between the drives and the trailer axles; moving the fifth wheel shifts weight between the steer and the drives. Neither changes the gross, so if the total is over, the only fixes are less freight or a permit.

Weight and the rest of the trip

Weight affects more than the scale. A heavy load burns more fuel, wears tires and brakes faster and can slow you below the flow of traffic on grades. Flatbed and machinery loads are where weight issues come up most often; our page on flatbed dispatch covers how we plan those loads.

Curious how big trucks get when road limits don't apply? Our guide to the biggest truck in the world compares mining giants with highway rigs, and the 18 wheeler guide explains where each axle sits on a standard rig.

Getting loads that scale legal

On our desk, your empty weight, trailer and axle setup are on file from the first call, so an offer that would put you over never reaches you as a good one. The yes or no is still yours, and the other free tools cover size, hours and fuel.

Sources: eCFR, 23 CFR 658.17 Weight (2026).