In American terms, a compact car is a classification of cars that are smaller than mid-sized cars but larger than the subcompact category of cars. These are known as family cars in Britain and fall under the C-segment in Europe.

The United States Environmental Protection Agency (EPA), for the US and the international models respectively, defines the current compact car size, as approximately 4,100 mm (161 in) and 4,450 mm (175 in) long for hatchbacks.

Passenger car classes are primarily defined on the basis of interior volume index or seating capacity, except the automobiles that are classified as a special vehicle.

For convertibles, these figures change to 4,400 mm (173 in) and 4,750 mm (187 in) long while sedans, estate cars, and station wagons.

Sports utility vehicles and multi-purpose vehicles and that are based on the structure of small family cars that are also known as compact MPVs and compact SUVs come with similar sizes that range from 4,200 mm (165 in) to 4,500 mm (177 in) in the U.S.

For international base models, these figures change to 4,400 mm (173 in) to 4,700 mm (185 in).

These norms change from place to place, for example in Japan, any vehicle that is 3,400 mm-4,700 mm long, 1,480 mm- 1,700 mm  wide, and 2,000 mm high and comes with an engine of 660 cc-2,000 cc are known as compact cars.

The term compact car in itself is a largely North American term that denotes an automobile that is larger than a subcompact car but smaller than a mid-size car.

The compact car segment in the US holds a world wide market share of sixteen percent and the segment is mostly dominated by import models.

The wheelbases of compact cars fall between 100 inches (2,540 mm) and 109 inches (2,769 mm).