Intrigued by the concept of a 'bra intervention' I looked up some of the old threads and have been inspired to measure myself 'properly'.
Under boobs 31"
Over boobs 36"
I am currently wearing a 32C having worn 34B for years despite my 'correct' cup size being an A according to all the charts and M&S (I found I just spilled out of an A cup especially at the sides).
I have little padding on my ribs so I presume the 32 band is OK though sometimes I feel is does ride up a bit at the back so maybe I should try a 30.
I thought a C cup was pushing it a bit but if I understand correctly my measurements mean I should be a DD cup?