According to the Children's Hospital of Pittsburgh, small intestines are about 22 feet long, while large intestines stretch only about five feet. Their names come from their diameters, not their lengths.
According to WebMD, the large intestine is about three inches in diameter, while its smaller counterpart is about a third its size. The Children's Hospital of Pittsburgh states the primary function of the small intestine is to absorb nutrients from food and send them into the bloodstream. The large intestines absorb water and salts from the material that passes out of the small intestines, according to the hospital. In addition, any leftover waste products pass through the large intestines and are eliminated.