Get help from a doctor now ›. 6.9 m: The average length of the small intestine in an adult human male is 6.9 m (22 feet 6 inches), and in an adult female 7.1 m (23 feet 4 inches). It can vary greatly, from as short as 4.6 m (15 feet) to as long as 9.8 m (32 feet)....Read more..9 m: The average length of the small intestine in an adult human male is 6.9 m (22 feet 6 inches), and in an adult female 7.1 m (23 feet 4 inches).