BRAS: EQUIVALENCE OF SIZES
A bust that is not sufficiently adjusted or on the contrary a little loose can be corrected with an equivalent size, that is to say a size immediately below or above. In this equivalent size, only the bust size varies, the volume of the cups does not change.
a) If the bust of the bra looks too small, you can choose the upper size with a lower cup size. For example, if you have an 85D, the equivalent size 90C will offer the same volume of cups, but will be less tight under the bust.
b) If the bust of the bra looks too big, you can choose the lower bust size with an upper cup size. For example, if you have a 90B, the equivalent size 85C will offer the same volume of cups, but will be tighter under the bust.