American Bra Size Average Increases From 34B to 34DD In Just 20 Years, Survey Says

[politicat]

5. Short answer: yes.

Long Answer: cup size (the letter part) refers to the conic section or hemispheric section. The design math gets pretty hairy (it's the one section of the industry where advanced math is absolutely required) and isn't helped at all by the fact that American bra manufacturers and retailers have an absolutely borked non-system of "sizing".

Standardized cup sizes are based on volume, but volume varies with chest-wall sizing (thus a 36B, a 34C and a 32D all use the same underwires or molded cups and have the same volume) and chest wall has little or nothing to do with either implants or obesity (there's not a lot of subcutaneous fat on the rib cage.) Further, bra sizing and fitting often still uses a system invented before modern elastics and stretch fabrics, which means a systematic failure. (Band size should be the exact measurement of the chest wall, not that measurement plus 2, 3, 4 inches.)

There's a huge sub-reddit on this. http://www.reddit.com/r/ABraThatFits/