Most women keep buying the same size of bra for years without taking into account slight variation in weight. Actually you must measure yourself every time you go to buy one. Your bra is small if your shoulder straps cut into your shoulders; the breast tissue is not fully contained in the cup of the bra and appears under the straps, side panels and over the top of the cups; or under band cuts into your body.
Your bra is too big if it rides up at the back and it shows wrinkles in the cup area, or the breast lacks support. You should choose a bra which has a firm elasticized edge to the cups and the strap is adjustable so that it can provide comfort and support.
While choosing a bra it is important that we determine the right size. Measure around your rib cage, just underneath your breast. Record the measurement. Add 5 to this number. Since bra sizes come only in even number, round off this number to the next even number.
Measure around the fullest part of your bust. To get the cup size you subtract the bra size from the breast size. Now check the table below to get the right cup size. It is imperative both for health and good form that you choose the right fit for your bra.