Its ok it can be very confusing because the old add inches method is found everywhere and this gives most women a very loose band and small cups so it is not effective for modern bras they are only just changing it so a lot of brands will list this calculator it doesn't mean it works for there brand its just the original recognised method.
About 30d/30dd/ 32c/32d should fit well the cups in Victoria secrets apparently run small if that helps I have never bought from there. but always better to try on bras for a perfect fit there is a lot of variation between brands and styles also you body/breast shape effects the size too.
The way to measure is take your under bust measurement 30 that is the band size it should be a nice tight fit you should only be able to fit a few fingers under it while wearing then the difference is the cup so d or dd but this is where you should try on i also said 32 because sadly its hard to find 30s I normally sew up my 32s smaller.
About 30d/30dd/ 32c/32d should fit well the cups in Victoria secrets apparently run small if that helps I have never bought from there. but always better to try on bras for a perfect fit there is a lot of variation between brands and styles also you body/breast shape effects the size too.
The way to measure is take your under bust measurement 30 that is the band size it should be a nice tight fit you should only be able to fit a few fingers under it while wearing then the difference is the cup so d or dd but this is where you should try on i also said 32 because sadly its hard to find 30s I normally sew up my 32s smaller.