I recently had my sizes checked. My band size changed and I tried to get the same cup size and it did not work. The girl said that if you go down a band size go up a cup size. I remember when I shopped with Payton they said that too. It totally worked. So a 34DD fit me pretty much the same as a 36D. The band was all the way on the last hooks on the 36 and the first on the 34. I always bought 40B. Wayyy wrong. They were so uncomfortable and I never knew why. Also the shape makes a difference too. I cant wear a complete full coverage. I need plunge. I don’t fill it out and there’s gaps but if I go down a size it’s too small. So I just get the plunge or Demi and I’m all good.