The three major determinants of breast appearance are size and shape of the individual breast and the position of the breast and nipple when standing in an upright position. The right versus the left breast of any woman is very often of different size and even a different shape. Although common, these differences are perceptible but not very great. Sometimes, surgical intervention is needed to equalize the breasts.
Breast asymmetry needs to be corrected surgically when breasts differ from each other in a bra cup size in volume. If breasts differ from each other in less than one bra cup size, it is not thought to be in need for surgery. But if a woman does not feel comfortable about it or experience some psychological problems due to it, correcting such breasts is recommended.