The Dimensions of a 48 FT Semi-Trailer: Length, Width, Weight & Height

It is important to know the dimensions of any trailer you might hope to use. The volume of a trailer, or how much it will fit, all depends on the size and type of trailer. Since trailers can vary so much in size, today we’ll just be discussing the dimensions of a semi-trailer that is 48 feet long.

A semi-trailer that is 48 feet long is generally about eight and a half feet, or 102 inches wide. The height can vary depending on the kind of trailer, but for a semi, it is usually 13.5 feet or 162 inches tall. These figures are all according to standards set by the federal government.

Going forward, we will go more into detail about the length, width, weight, and height of a semi-trailer and answer other questions you might have about semi-trailers.


There is a federal limit to how long and how short a certified motor vehicle can be which is determined by the FHWA or the Federal Highway Administration. A semitrailer can come in a few different combinations. The most common include truck tractor semitrailer, truck tractor semitrailer trailer, and grandfather semitrailer combinations. These all have different uses and can all include a 48-foot-long semitrailer.

Truck Tractor Semitrailer Combinations

The minimum length of a trailer in a truck tractor-semitrailer combination is 48 feet. The types of trailers are usually used to carry freight goods. A semitrailer is different from a full trailer because full trailers have a cab, but a semi-truck needs a trailer to have commercial cargo capacity.

Although there is a minimum length, the Federal Highway Administration does not specifically set how long a truck-tractor-semitrailer combination should be and it is mostly decided by state-set provisions. However, with that being said, these truck-tractor-semitrailer combinations cannot be longer than 65 feet.

Truck Tractor Semitrailer Trailer Combinations

A truck tractor semitrailer trailer combination consists of a semitrailer and a trailer connected. In this case, the semitrailer is usually around 28 to 28.5 feet long with the trailer behind it being the same length from 28 to 28.5 feet long. The minimum combined length of these trailers, as per the regulations of the federal government is 28 feet and together they cannot exceed the length of 65 feet. These are used for the same purpose as the truck tractor semitrailer combinations, which is to transport freight.

Grandfathered Semitrailer

The last combination of a semitrailer that we will discuss today is a grandfathered semitrailer. A grandfathered vehicle, like the grandfathered semitrailer, is not manufactured to transport many passengers and is manufactured outside of the United States, and meets foreign emission standards. The legal length of grandfathered semitrailers is determined state by state. Below is a table explaining the regulations for the length of grandfathered semitrailers in each state.

Dimensions of a 48 FT Semi-Trailer
StateMaximum Length of Trailer
(in feet)
Alabama53″ 6′
Arizona57″ 6′
Arkansas53″ 6′
Colorado57″ 4′
District of Columbia
(Washington D.C.)
Indiana48″ 6′
Kansas57″ 6′
Louisiana59″ 6′
New Hampshire48″
New Jersey48″
New Mexico57″ 6′
New York48″
North Carolina48″
North Dakota53″
Oklahoma59″ 6′
Puerto Rico48″
Rhode Island48″ 6′
South Carolina48″
South Dakota53″
West Virginia48″
Wyoming57″ 4′
Maximum Length Regulations by State


Dimensions of a 48 FT Semi-Trailer
Dimensions of a 48 FT Semi-Trailer

The Federal Highway Administration set a maximum width on certified motor vehicles and their trailers which is 102 inches or 8.5 feet in all states except Hawaii where the limit is 108 inches or 9 feet. Although these regulations do not apply to special equipment or machinery such as emergency, farm, construction, or military equipment, it does apply to semi-trailers.

These width regulations protect the semitrailer truck drivers, their cargo, and other drivers on the road. The federal government puts these regulations in place so that other cars can fit around it safely on the road.

It is important to remember that these dimensions and restrictions concerning the width of a semitrailer do not include mirrors or safety equipment which are needed to ensure that truck drivers and others remain safe on the road.


The weight of a semitrailer is very important because it affects the safety of the vehicle and others around it. All states except Alaska have a gross vehicle weight limit. How much a semitrailer can weigh depends on the strength of the truck and the type of axle it has. However, if the semitrailer is over 48 feet long, then its maximum weight is from 43,500 pounds to 45,000 pounds depending on the axles and spacing. A 48-foot-long trailer is generally three-axled.

Type Of AxleWeight Limit (in pounds)
Single Axle20,000 lbs
Tandem Axle38,000 lbs
Tridem Axle42,000 lbs
Gross WeightSingle Axle: weight (lbs.) – 20,000; distance: 8’1″ Minimum spacing*
2-Axle Group: weight (lbs.) – 38,000; distance: 3’6″ Minimum spacing
3-Axle Group: weight (lbs.) – 42,000; distance: 3’6″ Minimum spacing
4-Axle Group: weight (lbs.) – 50,000; distance: 3’6″ Minimum spacing
Maximum Weight for Type of Axle

With that being said, there are certain exemptions to the weight limits. These exemptions include the implements of husbandry, snow and ice tolerance, enforcement tolerance, traction, and weight shifting in axle groups and government-owned vehicles. If needed, drivers can also get permits for overweight vehicles, but they still have to be within safety and regulation requirements.


The standard height for a 48-foot-long semitrailer is a little over 9 feet tall. This measurement is for the interior height, but the full height of the trailer including tires and suspension is about 13 feet 6 inches. It is important that a semitrailer stays within certain height regulations because if they are too high, the negative effects can lead to accidents. Some of these effects include uneven or zigzag driving patterns at high speeds.

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