for a 34A your sister sizes would be 32B or 36AA, both of the bras would have about the same cup volume as your 34A, just a looser or tighter band.
What is a 28DD equivalent to?
Current Bra Size Sister Size Down Sister Size Up
---------------- ---------------- --------------
28DD 26DDD/26E 30D
28DDD 26F 30DD
28E 26F 30DD
28F 26FF 30E
What is a 42DDD equivalent to?
30 32 42
--- --- -------
30H 32G
42D
42DD
42DDD/E
What size is 36AA?
Is AA smaller than an A cup?
There is a difference of between 2cm and 2.54cm (depending on where you shop) between each cup size, so an AA is an inch smaller than A and DD is an inch bigger than D.
Is a cup size bigger than a?
The cup size, however, is the difference between your band size and your bust size. If your bust size is less than 1 inch bigger than your band size, you're a cup size AA. 1-inch difference = A.
How big is an AA cup?
1. Band size 2. Cup size
------------ -----------
AA
26
28
30 33.0-34.6