Most people would assume that a coupe is a two-door vehicle, while a sedan is a four-door vehicle. However, this is not always the case. The Society of Automotive Engineers (SAE) defines a coupe as a car with an interior space of less than 33 cubic feet, while a sedan is equal to or greater than 33 cubic feet. This means that coupes can have four doors and sedans can have two doors.
The difference between coupes and sedans is more than just the number of doors. While style and other aspects may differentiate them more markedly, size is the only thing that makes the distinction. For example, the Cadillac Deville coupe has metal edges that form part of the door and, when rolled up, the window is placed inside the frame. Some aerodynamic vehicles, such as the Mercedes CLS, Porsche Panamera and VW Passat CC, are marketed as coupes but are actually four-door sedans with an aerodynamic roof.
This can lead to confusion when it comes to defining the four-door coupe. Some consumers even compare them to two-door sedans. Sedans are considered more of a family car due to their larger interior space. Examples of two-door sedans include the Ferrari 612 Scaglietti, Mercedes CL-Class, Chevy Monte Carlo and Mazda RX-8.Whether or not to buy a four-door coupe depends on your budget, personal preferences and how often you have passengers in the back of the vehicle.
Ultimately, size is what makes the difference between a coupe and a sedan.