There is no single standard “width” measurement for an elephant's body in the wildlife references cited here. Common reference measures include shoulder height, head-to-body length, weight and chest girth; they vary by species, sex, age and individual.
If you mean ear width, an African elephant's ear can span about 5 feet across. Its ears are part of its visible profile, but this is not the width of its body. The International Elephant Foundation describes the ear dimensions, and the Smithsonian's educator guide notes African elephant ears can be about 4 feet across.
For body-size context, Smithsonian's National Zoo says adult Asian elephants typically stand 6 to 12 feet at the shoulder and weigh 6,000 to 12,000 pounds. These are species-level reference ranges, not a body-width measurement. See the Smithsonian Asian elephant profile.
How much space does an elephant need?
Wild elephant home ranges can be very large and vary greatly with food, water, habitat and the animals being tracked. Smithsonian data from radio-collared wild Asian elephants in Myanmar describe home ranges from about 6–20 square miles in some cases to 190–580 square miles in others. These are observed home-range areas—not a minimum-space formula, a captive-enclosure specification, or a recommendation for keeping an elephant.
An elephant's living space cannot be reduced to one area number from its body size. For any captive setting, consult current species-specific animal-care guidance, applicable rules, and qualified elephant-care professionals. Wild home-range data should not be used to imply that a smaller enclosure is adequate.
Source: Smithsonian's National Zoo: Asian elephant size and home ranges.