To be blatantly honest:

I am not a B cup.  I haven't been a B cup since I was at least 13 years old.  Possibly younger.  I've been large-breasted for much of my life.  So yesterday, when a good friend of mine told me the bra she had lent me for my halloween costume was a 38B (I had to make many modifications to this bra, it was very, very stretched out and very old, but once I had sewn it up a bit, it fit perfectly), I became very nervous.  Not that my breasts were actually smaller than I had originally thought, but that I was wearing the completely wrong bra size. Barenecessities.com gives a guide of how to measure your bra size, so I pulled out my tape measure and did some math.

My suspected bra size: 34D (though I know for a fact, I am a 32D, but it is rare to fine bras that are this size)
I measured the following:
Rib number = 31 (this was measured under my armpits and across the front part of my chest, not including my breasts) Which the website says to round up to 32, since a 31 bra is impossible.
Cup number = 33

By the calculations of the measuring guide, I should have 32A breasts, which is completely impossible. (i came up with this number by subtracting my rib number from my cup number.)
If I do not round, then my size is 32B.
Anyone who knows me can see that this is also very unlikely.
I distinctly remember trying on bras in Victoria's Secret with my sister when I was 14 or 15, a freshman in high school, and I needed a strapless bra to wear under my dance costume for the recital that year.  We went into the store and I picked out the size I thought I was: 34C.  When I went into the dressing room, I found that the bra was extremely uncomfortable, I was popping out of it, and I immediately began freaking out.  My sister brought me the next cup size up, the D, and poof, it fit perfectly.  I went home in tears.
I've since accepted that I am, in fact, my mother's daughter, and have inherited the Kurtz women's breasts.  However, things just don't add up to me being a B cup.  I could tolerate a C, definitely.  I would love to stay a C, bras are easy to find outside of specialty bra stores when they are 34Cs.  But what I don't understand is how I could possibly be a B cup when I haven't worn one for years?
I suppose I'll have to test this out when I go home for winter break in a few days.

I can't believe I just wrote a blog post about the size of my tits.  Shows I'm a helluva lot more comfortable with them now than I was 5 years ago.