We find many women are wearing a band that is too loose for them, and need to go smaller in the band and bigger in the cups. The band should provide 90% of the support so a band that is too big can cause some serious fit issues. It’s important to understand how the cup size is relative to the band when going up or down a size.
When going down in the band, you must go up in the cup to maintain the same cup size. For example, if you are wearing a 36C and need to go down to a 34 band, you will need a 34D to keep the cup size the same. The opposite also applies - you need to go up a band size, remember to go down in the cup.