To find the band size, one measures at the top of the rib cage, just below the base of operations, so to speak. To find the cup size, one measures across the landscape at its most extreme terrain. Subtract the difference to determine cup size.
It might surprise some to learn that cup sizes work as follows: A, B, C, D, DD, DDD, E, F, G, etc. At least that's how it worked where I went. 1 inch of difference is an A cup, two inches a B, etc. I was measured.
A 38G. Yes, my friends. The woman looked me in the eye and had the audacity to tell me, "You need a 38G." I had to pause as the wind blew back my hair and everything went to black and white for a moment.
Once my Russ Meyer moment had passed, I went to a dressing room, there to be met with a truly magnificent feat of structural engineering. This thing was padded and wired like a Miss America contestant with braces. I finally got it on and faced the reality:
I don't want my bra to fit if that's what it feels like. A tight, constricting band around my ribs while vast tracts of land brush my chin? No thank you. I tried on a few more, just to make us all feel better, then selected the same style of bra I have worn for years, but with a larger band and smaller cup. It fits fine.
I do admit, though, that I am tempted to buy the 38G as a prank. It would also make a fine dual crash helmet for when we take the children to the race track.