the number, which measures chest and back all the way around, has nothing to do with breast size at all - just some str8 guys think it does because it's the numbers on bras, and in their minds bras and breast size are the same thing. the cup size - A being small, C being around average, D being a little busty and DDD being pretty damned big - is the breast size.

i know some taller and heavier women who wear a 44B - which means big chest and back, smallish breasts - and slender women who measure 32DDD - small chest and back, large breasts.