Guide To Semi-Trailer Dimensions

When it comes to freight shipping, these tips will be the most definitive guide to common trailer dimensions found in the United States. This guide will help you in choosing the right trailer  size when considering a truckload shipment. We suggest that you save or print this document for future reference.

The Basics

According to Federal Law, a freight trailer is limited in size. The U.S. Department of Transportation regulates any vehicle when they are operating on interstate highways. There are hundreds of size combinations and even several state exceptions to the federal laws.
However, today, 99% of dry and refrigerated trailers come in 2 main sizes. Flatbed trailers come in about a half-dozen combinations.

Dry Vans and Refrigerated (Reefer) Trailers

A dry van and a refrigerated trailer arte basically offered in the same overall dimensions. The main difference between a dry van and a reefer is the cooling unit and the interal air chutes in the reefer.

Trailers will be either 48’ long or 53’ long. Today, about 80% of dry trailers and 60% of reefers are 53’ long. For delicate loads, you may want to ask for "pad wrap". However, be aware that these trailers are less common and will cost more. You do NOT need pad wrap in you palletize or box your load correctly and carefully. When calculation your trailer needs, order the most commonly available trailer if your load will fit. The most commonly available is a standard 48 foot long, 96 inch wide (internal dimensions) trailer or larger.

Flatbed Trailers

Flatbed trailers come in a variety of sizes compared to dry vans and Reefer trailers. Flatbed loads are often referred to as "specialized transport" because of the required expertise needed. The more specialized the trailer, the higher the cost. In the image below, the most common flatbed trailer is at the top and the least common is at the bottom.

Commercial Vehicle Weight Standards

National weight standards apply to commercial vehicle operations on the interstate highway system. If the truckload is off of the interstate highway system, states may set their own commercial vehicle weight standards.

Federal Commercial Vehicle Maximum Standards on IHS:

  • Single Axle: 20,000 pounds
  • Tandem Axle: 34,000 pounds
  • Gross VehicleWeight: 80,000 pounds

*For information regarding issuing of overweight or oversize vehicles, go Please note, these permits are not issued by the federal government but by the individual states.

Bridge Formula Weights

This formula helps you in determining the maximum allowable weight that any set of axles on a motor vehicle may carry on an itnerstate highway system, as well as limiting the weight-to-length ratio of a vehicle crossing a bridge. Please see below for the bridge formula:

  • W = overall gross weight on any group of two or more consecutive axles to the nearest 500 pounds
  • L = the distance in feet bwtween the outer axles of any group of two or more consecutive axles
  • N = the number of axles in the group under consideration