A 32B and a 34A have similar cup volumes on different band sizes so it's not surprising you can fit into both. I wear a 32DD but since that is hard to find I compensate by wearing a 34D (sister sizes). As for the cup volume of 30B that would be similar to a 32A and a 34AA so I don't know how you could fit into those sizes, different brands make different cuts I guess. A 36A on the other hand is similar in cup volume to that of a 34B and a 32C so it's very strange that you can fit into all of those sizes, but whenever you go to a store just always make sure to try on your bras and make sure they fit comfortably before buying them.

They have the same cup volume.

They're sister sizes.



KINDA.

Because you only ask 32B and 34A in your question initially. These 2 are sister sizes.



But a 30B is in no way the same cup volume as a 36A.

a 32B means 32 inches around the ribs and a B cup

a 32A means 34 inches around the ribs and an A cup



you can fit into both because 32B's band is smaller/the cup is bigger, but the 34A's band is bigger around the ribs.



they aren't the same though

They are close to the same but you can usually feel the slight difference.

They are very similar, especially in terms of actual cup volume. The main difference is that a 32B will fit a smaller ribcage than a 34A. Hope this helps.