Like band size, the cup size also differs slightly depending on each Country.
Generally, your cup size can be calculated by subtracting your under-bust measurement from your over-bust measurement. The over-bust measurement is taken from the torso over the fullest part of the breasts, with the crest of the breast halfway between the elbow and shoulder, usually over the nipples.
Common Mistake! We like to say that our breasts are like sisters…not twins. Your breast size changes and fluctuates throughout the year, and most women have one breast that's bigger than the other — so you shouldn't obsess over a number. Instead, focus on fit.
The cup should lay flat against the body. If there is gaping at the top of the cup, you probably need to try another style or go down a cup size. If your breasts are bulging out of the top of the cup, you need to go up a size.