Wearing the right size bra can decrease the number of other problems a girl will have with her bra. For instance, a bra that's the right size won't pinch, gap, or slide around. So it makes sense to spend some time learning about bra sizes.
There are two parts to a bra's size: the chest size (also called the band size) and the cup size. The chest or band size is represented by a number (32, 34, 36, etc.) and is the part of the bra that runs across a girl's chest and around her back. The cups are the parts of the bra that hold the breasts and come in letter sizes (AA, A, B, C, etc.).
Bras come in many sizes, which are different combinations of the chest sizes and cup sizes — 32AA, for instance. It's important to get both the chest and cup sizes right to ensure a proper fit. Some bra manufacturers are now starting to offer cup options in half sizes in addition to regular cups to help girls get a better fit.