The squirrel's total body length measures 45 to 70 cm (17.7 to 27.6 in), tail length is 20 to 33 cm (7.9 to 13.0 in), and they range in weight from 500 to 1,000 grams (1.1 to 2.2 lb). There is no sexual dimorphism in size or appearance. Individuals tend to be smaller in the west. There are three distinct geographical phases in coloration: in most areas the animals are brown-grey to brown-yellow, while in eastern regions such as the Appalachians there are more strikingly-patterned dark brown and black squirrels with white bands on the face and tail. In the south can be found isolated communities with uniform black coats
Eastern fox squirrels are most abundant in open forest stands with little understory vegetation; they are not found in stands with dense undergrowth. Ideal habitat is small stands of large trees interspersed with agricultural land. The size and spacing of pines and oaks are among the important features of eastern fox squirrel habitat. The actual species of pines and oaks themselves may not always be a major consideration in defining eastern fox squirrel habitat. Eastern fox squirrels are often observed foraging on the ground several hundred meters from the nearest woodlot. Eastern fox squirrels also commonly occupy forest edge habitat.
The fox squirrel's natural range extends throughout the eastern United States, excluding New England, north into the southern prairie provinces of Canada, and west to the Dakotas, Colorado, and Texas. They have been introduced to both northern and southern California. While very versatile in their habitat choices, fox squirrels are most often found in forest patches of 40 hectares or less with an open understory, or in urban neighborhoods with trees. They thrive best among trees such as oak, hickory, walnut, and pine that produce winter-storable foods like nuts. Western range extensions in Great Plains regions such as Kansas are associated with riverine corridors of cottonwood. A subspecies native to several eastern US states is the Delmarva fox squirrel (S. n. cinereus).