Band & Cup Sizes Explained

Often times during a fitting, I hear people exclaim “I’m a what?!” when I tell them the cup size portion of their measurement. “No, I can’t possibly be a (fill in the blank) cup!” Sound familiar? Part of this confusion arises from a long-standing misconception—propagated in part by the media—about how cup sizes relate to a person’s boobs. Celebrity bra size reports often reinforce stereotypes by associating a cup size with a certain breast size, leaving many women and men believing a DD represents an ample chest like Sofia Vegara’s or Salma Hayek’s or Jessica Simpson’s or . . . and the list continues. For what seems like forever, cup sizes have been regarded in this way:

A’s are flat, B’s are small, C’s are average, D’s are big, DD’s are huge, and DDD’s are ridiculous.

The truth is cup size mean absolutely nothing on its own. But, why? Cup sizes are only one half an old married couple, and it is their long-suffering partner, the band size, that gives the cup size any kind of significance. The little known fact to finding the right size bra is that cup sizes vary widely from one band size to another, i.e., a D is not a D is not a D.

Bras, like other fashion items, are built on the idea of scaling proportions, but the scale does not center on the cup—it’s the band that’s the star here. The band of the bra is designed to represent your torso girth with everything from the width of the cups to the placement of the straps to the length of the wings shifting with each size to ensure people receive a customized fit. As you step up in band size, the entire bra scales upward because the designer recognizes that the person wearing this band is proportionally bigger than the person who wears a smaller size. Thus, if a person wears too big a band size, fit issues ensue, such as the underwire extending too far on the sides, the band not snugly supporting the breasts, the straps being too wide set, and proportionally bigger cups requiring a smaller size to fit.

Note how the cup size continues to get smaller as the band size decreases.
Note how the cup size continues to get smaller as the band size decreases.

So, how do cup sizes factor in? Simply put, they follow a pretty straightforward formula although certain European brands will scale each cup size by centimeters instead:

A = Band Size + 1″, B = Band Size + 2″, C = Band Size + 3″, etc.

Nevertheless, because there is often a limited selection of sizes available, people will usually buy “cup size equivalent” bras—or bras whose sizes are vastly different but whose cups require the same amount of breast tissue to fill them. For example, all of these sizes are cup-size equivalents:

28G = 30FF = 32F = 34DDD = 36DD = 38D = 40C

And here is the heart of why cup sizes mean absolutely nothing without a band size to define them. The person who wears a 28DD, for example, has less breast tissue than the person who wears the 34DD. In fact, a 34DD is cup size equivalent to 28FF!

All of these bras are cup size equivalents.
All of these bras are cup size equivalents.

To demonstrate how the band and cup size work together, let’s examine the DD cup.  Below are some sample measurements for a person who might wear these sizes:

28DD = 28″ ribcage, 33″ chest
30DD = 30″ ribcage, 35″ chest
32DD = 32″ ribcage, 37″ chest
34DD = 34″ ribcage, 39″ chest, etc.

As you can see, each DD cup represents not only a completely different set of measurements but also a completely different sized person.  However, I do want to note that some people choose to size up in the band for comfort or health reasons.  For example, the person measuring a 28DD may actually prefer a 30 or 32 band, making the new cup size a 30D or a 32C.

The Moral of the Story:  Cup size cannot and should not be used as way of representing breast size.  All that matters is you find the bra size that fits, flatters, and feels comfortable to you! 

For more information on how band and cup sizing works, please check out the video below: