Determining your Cup Size
Step One: Find your underbust
Stand with your arms by your side and measure around your body, directly below the breast. Make sure the tape is straight all the way around and is as tight as possible without pulling at your skin.
This is how the underband of the bra will fit, so the tape should be tight, but not uncomfortable. It's best to take this measurement braless, or with a non-padded, underwire-free bra.
Step Two: Find your overbust
Measure around the fullest part of your breast (usually over the nipple). This is best done while you're wearing a non-padded bra. Hold the tape gently so that it is resting lightly on your body. Make sure that the tape measure is straight across your back, and sits parallel to the floor.