It’s so bad that my fiancée has some bras that say she’s a B cup and others that says she’s a D cup. In order to go bra shopping, you have to actually try them on to find out if they fit.
If I had to try on underwear to see if they fit, I might not bother with underwear at all!
It’s because whatever maniac invented the sizing scheme decided that every letter represents 2 inches more around your body at the weirdest boobage point than just below it. What a bonkers system! A woman with 38B bras is 38 inches around at the band, and 40 inches around at the girls. Nonsense. The way dudes THINK it works makes so much more sense.