Truck weight limit checker for axle groups and gross weight

The federal truck weight limits

On the Interstate system, four federal limits apply to every truck:

• Gross weight: 80,000 lb for the whole vehicle, unless the bridge formula sets a lower number. Source
• Single axle: 20,000 lb on any one axle. Source
• Tandem axle: 34,000 lb on two axles spaced as a tandem. Source
• Bridge formula: a limit for any group of two or more axles based on the number of axles and the distance between the outer ones. Source

The checker tests each axle group against its limit, then tests the gross against both 80,000 lb and the bridge formula for the whole vehicle, using the overall distance from the first axle to the last. The lower of the two is your legal gross.

One exception matters for semis: two consecutive tandems can carry 34,000 lb each when the first and last axles of the two tandems are 36 ft or more apart. Source That is what lets a standard 5-axle tractor-trailer reach 80,000 lb.

Worked example: a 5-axle van at the scale EXAMPLE

The scale ticket reads 11,500 lb on the steer, 33,500 lb on the drive tandem and 33,000 lb on the trailer tandem, for 78,000 lb gross, with 51 ft from the steer axle to the last trailer axle. Every group is inside its limit and the gross is under 80,000 lb: legal.

Now the same load with the trailer tandems slid forward so the overall distance is 40 ft. The bridge formula for five axles over 40 ft allows far less than 80,000 lb, so the same 78,000 lb load becomes overweight. Sliding the tandems back fixes it. That is why drivers slide tandems at the scale.

Axle weight calculator: reading your scale ticket

A certified scale ticket usually shows three weights for a semi: steer, drive and trailer. Enter them as they appear. If one group is over and the gross is fine, the load is sitting in the wrong place: slide the fifth wheel to move weight between steer and drives, or slide the trailer tandems to move weight between drives and trailer.

If the gross is over, no amount of sliding helps. The load needs to come off, or the move needs an overweight permit from every state it crosses.

Box truck and straight truck weight limits

For a straight truck, the truck's own GVWR is usually the limit that bites first. A 26 ft box truck rated 26,000 lb may not weigh more than that loaded, even though its axles could legally carry more on the Interstate. Payload is the GVWR minus the truck's empty weight, which is often far less than drivers expect once the liftgate and body are counted.

Dump trucks and other multi-axle straight trucks are different: their rear groups often run near the bridge formula limit, so the spread between axles matters. Use the tri-axle setting in the checker for those.

When you need an overweight permit

Some loads can't be made legal by moving or removing weight, such as a single heavy machine that can't be split. Those move on overweight permits issued by each state on the route, often with route restrictions, extra axles and bridge checks. A permit doesn't raise every limit; it allows a specific load on a specific route under specific conditions.

Weight mistakes that cost drivers

• Trusting the bill of lading. Shippers estimate. Scale the load before a long run.
• Ignoring fuel weight. A full set of tanks can be the difference on a load near the limit.
• Forgetting the tandem slide. A legal gross can still fail on a single group.
• Assuming state roads match the Interstate. Off-Interstate limits and posted bridges can be lower.

What the result means

Green means legal on the federal Interstate limits for the weights you entered. It doesn't cover state roads, seasonal frost limits or a lower posted bridge, and it doesn't replace a certified scale. Red on a group means move the weight; red on the gross means remove weight or get a permit.

When you dispatch with us, your truck's ratings and axle setup sit on your rig card, and we check each load's weight before we call. A load that would put you over never reaches your phone. See how that works in our dispatch for owner-operators.