In the United States, a minicompact car is defined as one with a cargo volume index of less than 85 cubic feet. Subcompacts have dimensions of 85 to 99.9 cubic feet, compacts 100 to 109.9 cubic feet, midsize cars from 110 to 119.9 cubic feet, and large cars have dimensions of 120 cubic feet and above. Two-seaters do not have defined measurements, but they are classified as any vehicle with only two designated seating positions.
It is a common belief that the exterior dimensions define the class size of a vehicle, but in the United States, this is not the case. The U.S. Environmental Protection Agency is the government body in charge of classifying vehicle sizes, and it determines a car's size classification by interior passenger and cargo volume. Thus, a Hyundai Veloster and Rolls Royce Phantom are both in the compact category, a Bentley Continental GT Convertible and Chevrolet Spark are classified as subcompacts, and an Aston Martin DB9 and Fiat 500 fall under the minicompact category.
The United Kingdom and the rest of Europe follow a different way of classifying vehicle sizes. There, the exterior length of the vehicle does define its market segment. The popular import Mini Cooper Clubman belongs to the Euro B-Segment of small cars, which is for vehicles about 12 to 14 feet long. In the United States, the Mini Clubman falls under the compact class, which is comparable to the medium cars segment in the United Kingdom.