The human appendix averages 9 cm in length but can range from 2 to 20 cm. The diameter of the appendix is usually between 7 and 8 mm. The longest appendix ever removed measured 26 cm from a patient in Zagreb, Croatia.The appendix is usually located in the lower right quadrant of the abdomen, near the right hip bone.The base of the appendix is located 2 cm beneath the ileocecal valve that separates the large intestine from the small intestine.he appendix is usually located in the lower right quadrant of the abdomen, near the right hip bone. The base of the appendix is located 2 cm beneath the ileocecal valve that separates the large intestine from the small intestine.