Now I'm no expert in this field, but I was always under the impression that the bigger your boobies are, the bigger the letter (A, B, C, D, etc.) and looking down at mine they definitely don't strike me as an 'A'. According to those two sites I linked above, it seems they're not basing the letter size (or I guess it's called the cup size) on the actual size of the breasts but rather on the difference between the circumference of the bust line and the circumference right under the bust line.
So...does anyone know if this is the actual right way of measuring? Or did I screw it up completely?