What does 45:55 mean to you? A recent study of 1,315 women and men of varying ages and ethnicities reveals 45:55 as the overwhelmingly most popular breast proportion. The numbers represent 45 percent of breast tissue above the nipple and 55 percent below. Using an electronic photo altering technique, researchers modified the balance of various models. A ratio of 45:55 was favored by 94 percent of plastic surgeons, 90 percent of men, and 87 percent of women in their 30s. Research like this aids your surgeon in making appropriate cosmetic surgery recommendations to help you plan your transformation.