How much a semi-truck weighs: 80,000 lb, the axle limits and the bridge formula

An empty semi-truck, tractor and van trailer together, weighs roughly 30,000 to 33,000 pounds (13,608 to 14,969 kg), by our own addition of two figures in a 2010 National Academies report, which puts a representative Class 8 sleeper-cab tractor at 16,000 to 19,000 pounds (7,257 to 8,618 kg) and a non-refrigerated van trailer at about 14,000 pounds (6,350 kg). Hyundai Translead lists its 53-foot dry vans at 13,350 to 13,855 pounds (6,055 to 6,285 kg) empty, and Kenworth said in 2014 that a lightweight-specified T680 with a 52-inch mid-roof sleeper had a scale weight close to 15,000 pounds (6,804 kg). Loaded, the federal limit on the Interstate System is 80,000 pounds (36,287 kg).

Empty weights and the loaded limit, with the source of each figure:

Vehicle	Weight	Source
Class 8 sleeper-cab tractor, representative, empty	16,000 to 19,000 pounds (7,257 to 8,618 kg)	National Academies report, 2010
Kenworth T680 52-inch mid-roof sleeper, lightweight specification, scale weight	close to 15,000 pounds (6,804 kg)	Kenworth, as reported by Bulk Transporter, June 2014
Van trailer, non-refrigerated, typical	about 14,000 pounds (6,350 kg)	National Academies report, 2010
Hyundai Translead 53-foot dry vans, four models	13,350 to 13,855 pounds (6,055 to 6,285 kg)	Hyundai Translead product pages
Loaded vehicle, federal gross limit on the Interstate System	80,000 pounds (36,287 kg)	23 CFR 658.17

A loaded semi-truck may weigh at most 80,000 pounds on the Interstate System under federal law, with no more than 20,000 pounds on any single axle and 34,000 pounds on a tandem axle, and the federal bridge formula can set a lower total depending on how many axles the truck has and how far apart they are. The limits include all enforcement tolerances. They apply to the loaded vehicle: federal law sets no empty weight for a tractor or a trailer.

Status: 30 September 2026. This page follows 23 CFR 658.17 as published in the eCFR with the issue date of September 23, 2026, the text of 23 U.S.C. 127 in the 2023 edition of the United States Code, and the Federal Highway Administration’s pamphlet Bridge Formula Weights (FHWA-HOP-19-028, August 2019). FHWA says the pamphlet paraphrases the statute and the regulation for illustration only and that they take precedence in a dispute. The federal limits apply to the National System of Interstate and Defense Highways and reasonable access to it; State limits on other roads are not covered.

The federal weight limits

Section 658.17 also stops States from going below these figures on the Interstate System. States may not enforce limits of less than 20,000 pounds on a single axle, 34,000 pounds on a tandem axle, or the bridge formula weights, up to a maximum of 80,000 pounds including all enforcement tolerances. They may not limit tire loads to less than 500 pounds per inch of tire or tread width, except on the steering axle, and may not limit steering axle weights to less than 20,000 pounds or the axle rating set by the manufacturer, whichever is lower. How a weight differs from a manufacturer’s weight rating is explained in truck weights: GVW and GCW.

No hidden tolerance. The gross, axle and bridge formula weights are “inclusive of all tolerances, enforcement or otherwise”. The one exception is a scale allowance factor when portable wheel-load weighers are used: the regulation puts their accuracy generally within 2 or 3 percent and says an allowance above 5 percent may never be applied. A fine schedule that imposes no fine up to a threshold, the regulation’s example being 1,000 pounds, is treated as a tolerance that 23 U.S.C. 127 does not authorize.

The bridge formula

FHWA says Congress enacted the Bridge Formula in 1975 to limit the weight-to-length ratio of a vehicle crossing a bridge, either by spreading weight over more axles or by increasing the distance between them. As trucks grew heavier, allowable weights were linked to the number and spacing of axles, because a short vehicle concentrates the same weight on a smaller part of a bridge than a longer one.

The statute writes the formula as W = 500 (LN/(N−1) + 12N + 36), where:

• W is the overall gross weight on any group of two or more consecutive axles, to the nearest 500 pounds;
• L is the distance in feet between the extreme, or outer, axles of the group;
• N is the number of axles in the group.

Every group of two or more consecutive axles must comply, even when the single axles, tandems and gross weight are within their limits. On a five-axle tractor-semitrailer that means the whole vehicle (the “outer bridge”), the tractor (axles 1 to 3) and the trailer group (axles 2 to 5). FHWA’s pamphlet says experience shows these three combinations are the critical ones; if they are satisfactory, the others on that type of vehicle normally will be. It also notes that the single-axle limit replaces the formula for axles not more than 40 inches apart and the tandem limit replaces it for axles over 40 and not more than 96 inches apart; at 97 inches apart, two axles may carry 38,000 pounds and three axles 42,000 pounds.

FHWA’s worked example. A five-axle tractor-semitrailer carries 12,000 pounds on the steering axle and 17,000 pounds on each of the four axles of the two tandems, 80,000 pounds in all. Every single axle, tandem and the gross weight are within the limits, so the pamphlet checks the bridge groups:

In the last group the actual weight exceeds what the formula allows, so either some load must be removed or the 35-foot spacing increased. The pamphlet’s second example is a four-axle single-unit truck of 57,000 pounds that passes on axles 1 to 4 (57,500 pounds allowed at 23 feet) but fails on its three rear axles: 45,000 pounds against 42,500 pounds allowed at 9 feet.

The 36-foot exception. Two consecutive sets of tandem axles may carry 34,000 pounds each if the overall distance between the first and last axle is 36 feet or more, and in no case may the total gross weight exceed 80,000 pounds. FHWA’s example is a five-axle tractor-semitrailer carrying 34,000 pounds on both the tractor tandem (axles 2 and 3) and the trailer tandem (axles 4 and 5), provided axles 2 and 5 are at least 36 feet apart. The statute keeps a 30-foot figure for a motor vehicle hauling a tank trailer, dump trailer or ocean transport container before September 1, 1989. Which axle arrangements carry these names is explained in axle configurations explained.

When more than 80,000 pounds is allowed

The federal limits have a few exceptions, each set out in 23 CFR 658.17 or 23 U.S.C. 127:

• Nondivisible loads. States may issue special permits without regard to the axle, gross or bridge formula requirements for nondivisible vehicles or loads.
• Grandfather rights. The single-axle, tandem and gross limits do not apply to weights legally authorized under State law on July 1, 1956, and the axle-group requirement does not apply to vehicles grandfathered under State axle-group tables or formulas on January 4, 1975. FHWA says Interstate weight limits in some States may be higher for this reason.
• Idle reduction. A vehicle using an auxiliary power unit or idle reduction technology may be allowed up to an additional 400 pounds in gross, axle, tandem or bridge formula limits, if the operator can prove the unit’s weight by written certification and show that it is fully functional; the extra weight may not exceed 400 pounds or the certified weight, whichever is less.
• Named routes. The regulation and the statute list a small number of route-specific exceptions, such as Interstate Route 68 in Allegany and Garrett Counties, Maryland, for certain coal, log and pulpwood haulers, and Interstate Routes 29 and 129 around Sioux City, Iowa.

What about the empty weight?

Neither the regulation nor the statute sets an empty weight for a tractor or a trailer; they limit what the loaded vehicle may weigh on the Interstate System. The 12,000-pound steering axle and 17,000-pound tandem axles in FHWA’s example are an illustration of a loaded vehicle, not a standard. The empty weight depends on the tractor, the trailer and their equipment.

The National Academies’ 2010 report Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles, by the Transportation Research Board and the National Research Council, says a representative Class 8 sleeper-cab tractor will weigh 16,000 to 19,000 pounds and a non-refrigerated van trailer will typically weigh about 14,000 pounds. Hyundai Translead lists four 53-foot dry vans, each with a gross vehicle weight rating of 68,000 pounds (30,844 kg), at 13,350 pounds (6,055 kg) for the Composite, 13,460 pounds (6,105 kg) for the Composite XT, 13,510 pounds (6,128 kg) for the Original and 13,855 pounds (6,285 kg) for the HY-Cube, labeled as standard or tare weight.

Kenworth said in June 2014, as reported by Bulk Transporter, that a lightweight-specified T680 52-inch mid-roof sleeper it exhibited at that year’s Mid-America Trucking Show had a scale weight close to 15,000 pounds. The weight-reducing components it named included the 12.9-liter PACCAR MX-13 engine, an Eaton Fuller Advantage-series transmission, a 6x2 drive axle, wide-base single rear tires, aluminum rear wheels, air disc brakes and an aluminum fifth wheel.

What this page does not cover

• State weight limits on roads outside the Interstate System, and State weight tables that were not read for this page.
• Fines, weigh station procedures and how scales are operated.
• Payload advice.
• Overweight permit procedures in detail.