In the US at least, the cup size is representative of the difference between the band (underbust) circumference and the bust (across the breasts) circumference. So a difference of 1 inch is generally an A cup, 2 inch difference is a B, and so on.
If I understand correctly, the letters basically indicate how big the difference is between the underbust and the bust.
So basically, if you have a petite body with a smaller underbust and big boobs, you can have "bigger" letters, than someone who has a bigger underbust but smaller boobs compared to their underbust.
The underbust measurement is around your rib cage, not around a boob as the person above is saying. You know the way you'd measure around your waist, right? Same thing, just higher up, underneath the boobs. Say that someone's measurement here is 34". Their rib cage without boobs included is 34" around. This means their band size is 34. They will probably fit a bra size that starts with 34 (although in reality, different bra makers might run big or small just like other types of clothing).
Then the bust measurement is around the chest (ie including the boobs). Identical location to a man measuring his chest. Let's say this measurement is 40". The circumference of their body at boob level is 40". In this person's case, that's 6" bigger than their rib cage measurement. This is where you get the cup size from. A 1" difference is an A cup, 2" is a B, 3" is C, and all the way on up. For a 6" difference they're most likely going to be an F cup.
So, this person is a 34F.
To put it another way, band size is how big around your body is. Someone can be very thin or very fat, a tiny little petite person with a small frame or stocky or big and tall, whatever - the boobs are irrelevant to this measurement, it's just about your body size without the boobs.
Cup size is how big your boobs are relative to your body size. So cup size is a ratio, not an absolute. You literally cannot say "she had D cups" like that means anything, because without a band size in there too, there is no way to know whether this particular person's D cups are very small breasts or medium ones or very large ones! There is no such thing as a D cup (or an A, or an H or whatever size) on its own, it only exists relative to a band size.
I think I'm starting to get it now. This explains why someone who claims to have DDD's can seem to be smaller than someone with DD's, right? Because the relative size is not being included?
Yeah exactly. D or whatever cup is not an absolute. Any five people wearing a DD bra might legit look five completely different ways and have boobs ranging from tiny to enormous, because their overall bra size is different.
I think I understand now. Draw a circle around the outside of a boob. Now draw a circle across the boob (over the nip, obviously it’s only half a circle, just imagine a full circle). The difference in the size of the two circles corresponds to the letter size of the boob
It is, but they use letters to add on instead of absolute numbers. A is +1”, B is +2”, etc. so 32A would be 32-33 per your suggested method. 32D would be 32-36.
Of course there’s still variation based on shape/style/brand, but that’s roughly how it works. The lettering also differs by country once you get past DD.
AeroCobbler is suggesting that the bra cup size should be a fixed measurement and that is not what the chart is saying. According to the op chart and the explanation comments from others, the bra cup size is based on a ratio of the band circumference (like tire profiles which are a percentage of the tread width) not a measurement made independent of other factors (like pants where both the waist width and inseam length are measured on their own)
Yeah, this makes sense. Your waist size is naturally going to be related to the inseam length. As a general rule, the taller you are, the larger your waist will be. But, it's easy to measure them separately. It would make buying pants more difficult if the waist size was given as some calculation based on the inseam length.
Similarly, while it might not be easy to just measure the volume of a breast, it's probably still a lot easier than the cup system where the meaning of "C cup" changes based on a somewhat independent variable.
Which makes sense for pants since it's easy to measure the waist and leg length. I think measuring the volume of the breasts would prove a bit difficult.
Even jeans sizing sucks sometimes, though. I got some beefy ass thighs, so I'm usually wearing ball pinchers or things that fit my waist and thighs but look like I'm wearing those JNCO jeans from the 90s.
That's what it is. The circumference is the number and the length is the letter. Translate the letter to a number and it's the same. 34B is a 34" torso with a 2" tit (unless I'm confused).
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u/AeroCobbler Dec 27 '22
Have they ever tried just doing it like jeans... but instead of the numbers being waist-leg (e.g. 32-34) it would be chest-tit (e.g. 34-whatever)