In an infant, the heart is about one thirtieth of total body weight. In an average adult, the heart is about one three-hundredth of total body weight; this equals about 11 ounces (310 grams) in males and 8 ounces (225 grams) in females.

Heart size varies with body size. The average adult’s heart is about 5.5 inches (14 centimeters) long and 3.5 inches (9 centimeters) wide, or approximately the size of one’s fist. The heart is located just above the diaphragm, between the right and left lungs. One-third of the heart is located on the right size of the chest, while two-thirds are located on the left side of the chest.