So I measure my band, 38", say. Then I lean forward 90 degrees with no bra and measure across the flop of my boobs. That gives 42", and, I think, a D cup.
But a 38 D has cups which are far too close together for me. Surely the cup centres should align with my nipple spacing (imagine a bullet bra).
I can see that a pushup bra would attempt to press the boobs together, but is there also a relationship between band size, cup size and cup spacing?