What is a Double D Bra Size? The double D bra size, often denoted as DD, represents a cup size that falls between a D and an E. It is a common cup size for women with larger. 16 juin 2016 · There is a lot of confusion about bra fit and cup sizes mostly revolving around the letter D, there is this fantastic myth that a DD is HUGE and that anything at or beyond is a massive cup size when in reality a DD is roughly a 5” difference between your ribcage measurement (taken right underneath your breast tissue, not above your breast tissue, not adding inches to your measurement, not.