How to take your measurements...
To find your correct size, use a tape measure and take the following measurements. Stand with your back straight in front of a mirror, to ensure that you measure correctly and that the tape measure is kept level.
Measure under your armpits, around your shoulder blades, and over the fullest part of your bust. Don't pull the tape measure too tight. For fitting a bra, you also need to measurement just under your bust.
Measure around your natural waistline. This is the narrow part of your waist, about an inch above your navel. Relax and breathe out before your measure.