Wire circumference is crucial, Sandra says. Your underwire should surround and support your breast—not poke into it! If the wire pulls away from the body in the center, then the cup size is too small.

To test your underwire, Sandra says you should sit down when trying on a bra. That's a great way to make sure your bra isn't pulling away from your body. The cups should be secure against the breasts with the center of the underwire flush against the cleavage area.