Let me preface this by saying I am a man, and smoked a little too much, so I’m sitting here thinking… what is or was the original purpose of a bra? Weight support? Vanity? Covering the nips so people’s eyes met your eyes and you can have a normal conversation? Like what’s it all about?
Someone already mentioned that cup size has no meaning without band size, but also want to help dispel the myth that D is a “huge” size.
The rule of thumb is that your cup size is the difference between the size of your rib cage and the size around your chest. Then it’s 1” per cup, with caveats and adjustments, but we’re talking basics.
So in reality a C cup is a 3” difference between ribcage and breasts. That’s pretty modest. However in media, it’s often played up that DD is your Playboy model size, but those are more likely to be a G cup or larger, at least if they were sized correctly.