Follow the steps below to ensure that your band and cup sizes are correct.
Take a measurement of your band. Wear a lightly lined (non-push-up) bra to keep your breasts as natural as possible. Wrap a measuring tape around your breasts immediately. Check that it is parallel to the bottom of the bra band.
Now, take your bust measurement. Apply the tape to the fullest region of your bust. Check that it is still parallel to your band.
To determine the correct cup size, subtract your band size from your bust size. Each inch equals one cup size larger.