Although it's a term that we've used quite frequently, not many know what actually makes a car full-sized. According to the EPA's standards on automobile classes, all vehicle types are measured according to their interior volume. Note, that this combines both the cargo space and passenger room. With that being said, the EPA classes full-sized cars based on an interior volume of 120 cubic feet, or 160 cubic feet for station wagons. Vehicles that feature or surpass these sizes are considered full-size cars. Comparatively, a step down from that would be mid-size cars. The EPA's classification calls for a combined interior volume of between 110 to 119 cubic feet. Also, for a car to be mid-sized, the EPA has limited its maximum length to 196.8 inches.