Current compact car size, for US and international models respectively, is approximately 4,100 mm (161 in) and 4,450 mm (175 in) long for hatchbacks, or 4,400 mm (173 in) and 4,750 mm (187 in) long for convertibles, sedans (saloon) or station wagons (estate car). Multi-purpose vehicles and sport utility vehicles based on small family cars (often called compact MPVs and compact SUVs) have similar sizes, ranging from 4,200 mm (165 in) to 4,500 mm (177 in) in the U.S., and from 4,400 mm (173 in) to 4,700 mm (185 in) in international-based models.

During the 1960s, compacts were the smallest class of North American cars (and much bigger than those elsewhere), but they had evolved into only slightly smaller versions of the 6-cylinder or V8-powered two-bench six-passenger sedan. They were much larger than imports by makers such as Volkswagen and Datsun, which were typically five-passenger 4-cylinder engine cars, even though ads for the Ford Maverick and Rambler American would make comparisons with the popular Volkswagen Beetle. In the early 1970s, the domestic automakers introduced even smaller subcompact cars that included the AMC Gremlin, Chevrolet Vega, and Ford Pinto.

The 1977 model year marked the beginning of a downsizing of all vehicles, so that cars such as the AMC Concord and the Ford Fairmont that replaced the compacts were re-classified as mid-size, while cars inheriting the size of the Ford Pinto and Chevrolet Vega (such as the Ford Escort and Chevrolet Cavalier) became classified as compact cars.

Class Minicompact car Subcompact car Compact car Midsize car Large car Small station wagon Midsize station wagon Large station wagon Interior volume index (cubic feet) under 85 85-99.9 100-109.9 110-119.9 120 or over under 130 130-160 over 160 In the 1985 model year, compact cars classified by the EPA included Ford's Escort and Tempo, the Chevrolet Cavalier, Toyota Corolla, Acura Legend, Mercedes-Benz 300, Nissan Maxima, and Volvo DL.

In North America, the compact segment is still discernible as a class smaller than the average car but larger than the smallest models on the market. The Chevrolet Cobalt would be an example. The term has also been adopted to describe small SUVs, such as the Ford Escape.

United States Environmental Protection Agency (US EPA) has another set of classification rules based on interior passenger and cargo volumes.