The difference between the band measurement and the breast measurement is your cup size. Every two inches of difference is a cup size. For instance, my band is 40" (actually forty-and-a-half, but round down for give in the elastic of the bra); and my bust measurement is 45". That makes me between a D (which would be 44") and a DD (46"). In truth, one breast is a D and one is a DD. (Also keeping in mind that if you're like me, and your cup size doesn't change when you lose/gain weight - as your band size changes, your cup size will as well. I wear a larger cup size when I'm thinner, for example, because the difference between my band and bust measurements increases).
That's where a professional tailor or lingerie fitter comes in - they can eyeball small anatomical differences and tell you whether (still using my measurements as an example) a D or a DD would be better, and when to go up/down a cup size or when to make adjustments in the band size itself. But if you can measure yourself, or have a friend do it, you can experiment and see what's comfy for you. I wore a C cup and a band size that was FAR too large for me for many, many years before I learned to do this; the reason we HAVE bra fitters is that most women do the same. When in doubt, try on a larger cup and a smaller band than you normally wear.
This segment brought to you by the letter N for nerd."
- It's not an exact formula, and
- It's not going to work for every single person, since every person's body is a bit different.
The formula, however, is also easily adaptable for very-fitted SCA garments like cotehardies and "period brassieres", for example. The more information you know about how to fit your breasts, the more information you'll have about fitting them into a garment, whatever your underwear of choice.
Another thing many women tend to overlook, both with bra fitting and with costumery, is that your "breast" covers more area than just what you think of as your "boob."
|original diagram from THIS ARTICLE at NursingCrib.com|
Take a look at the purple lines I've added to the above diagram. For fitting purposes, you need to know that your breast, in a bra or a very tailored garment, begins at the side line of your body directly underneath your armpit; and also goes up to the point under your collarbone between your shoulder and the hollow of your neck. (This is especially true for larger-breasted women, since both modern bras and supportive SCA garments push the breasts upward towards that point).
* Also, keep in mind that if your breasts don't happen to be the ones that you grew yourself, sometimes the side-line will be moved forward, or be entirely absent, depending upon how your current model was installed by your surgeon.
Just as when fitting the cup size for a modern bra and taking into account the underarm/side area so that the bra cups support the whole breast and not just the "boob" on the front of your body; when fitting a supportive cotehardie or other supportive garment, you must take into account, in your alterations and pattern construction, the fact that your body pieces will need to support that area as well as everything else. This is why the line of tension in a self-supporting garment goes from that side seam to the front center of the garment, like this:
|Here, the blue line is the tension line. The red circle is the placement of the|
lifted and supported breast in such a garment.
And DO keep in mind that ALL of this is going to change from individual body to individual body, and your mileage may vary. In general, though, I hope this information helps you in your fittings.