I have just visited half a dozen websites with bra size calculators on them. The good news? These sites all have their own code for the calculators, so there have been at least six different codewriters gainfully employed in that industry, at one time or another. Bad news? Every calculator gave me wildly different results. The band sizes ranged from 36 to 40, and the cup sizes–hold on for it–from A to DD. Yes, one calculator told me to go for a 40A, another for a 36DD; the others ranged in between. WTF? I guess I have been living in a happy middle ground, at 38C.
Lesson: IT’S ALL A SCAM! You have to try on every bra in the store. Tell that to the salesladies.
Have you considered making your own bras? You could learn how to make a bra, and then make one that fits perfectly to your and only your breasts. You’d never have to buy a bra again.
Funny, I have never used an on-line calculator. I learned one way, with one little mistake (you add either 4 or 5 to the measurement to get the band size so you end up with an even size . . . I missed that step and thought I wore like a 27 M, or something). this thread had a lot of info . . .