How much bigger bra size is 38FF the 34d?

A 38FF bra size is generally considered larger than a 34D. The difference in band size (from 34 to 38) means that the 38FF has more volume in the cup as well. The letter size (D to FF) indicates that the cup in 38FF is also larger, making it a more substantial size overall. Generally, a change of one band size adjusts the cup size by one letter, so the combination of both band and cup size indicates a notable increase in size.