This is a formula that may be helful to those of you who are trying to find the right cup bra size. I used to work at Victoria's Secret selling Italian bras, and I used this quite accurate formula:
*Take a flexible tape measurer(with inch increments), and wrap it around your ribcage right under your breasts. Make it snug, not loose, but not uncomfortably tight. See where the beginning of the tape meets the rest of the measuring tape. Average ribcage sizes are between 28-40. If it's something like 31 1/2...consider it 32. You can always adjust your bra tighter if need be.
*This is your Band Size.
*Take the tape again, and wrap it around your back and across the fullest part of your boobs. Make sure the section that is behind your back isn't drooping down. Again, pull it snugly to your body,but not so much that it feels tight at all. See where the beginning of the tape meets the rest of the measuring tape. It should come out to be nearly the same, or a higher number than your Band Size measurement. This is your Cup Number.
*If your Cup Number is up to or around 1 inch bigger than your Band Size, you are probably a AA or A Cup.
*If your Cup Number is about 2 inches bigger than your Band Size, you are an A or small B Cup.
*If your Cup Number is about 3 inches bigger than your Band Size, you are likely a full B or small C Cup. Approximately every inch that increases, your Cup Size increases.
**Examples**
**So, if your Band Size is 28, and your Cup Number is 28 1/2 or 29, you should try on a 28AA or 28A size bra.
**If your Band Size is 30, and your Cup Number is about 32, you should try on a 30A or 30 Nearly B size bra.
**If your Band Size is 36, and your Cup Number is 37, you should try a 36A
Also, no two girls' breasts are alike. Some are fuller for their measurement size, some are placed farther apart, some are higher, some are lower...this all affects how bras will fit you. No matter how you are shaped, you are normal! This just means that you should try on a few different bra styles of the same size, or even a bra of a different but similar size to what you are measured to be.
When you wear a bra, you should not have any gaps between your boobs and the top of your bra cups. This means your bra cups are too big, or your straps are adjusted too loosely. Also, your boobs should not spill out the sides, or pop out of the top of your cups. This means your Band Size is correct, but that your cups are too small. If this happens when you are wearing a 32A, try a 32B. 32B is my size, and while it can be difficult to find, I love it because it has large enough cups, but a small Band Size.
I hope you find this helpful in determining the right bra for you!