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The BCD Method of Measuring Explained

July 1, 2018Your Fairy Bra Mother

When I first started designing bra patterns, I was faced with a dilemma – what sizing system should I use? Some patterns want you to take the full bust measurement, the high bust measurement and subtract the two to find your cup size. Still others want the rib cage measurement plus a “magic number” they pull out of the sky (could be 3, 4 or 5) to determine your band size.  There are actually FOUR ways of measuring for a bra and I talk about them in this blog (Four Ways of measuring). But for my patterns, I asked myself if I should use the actual rib cage measurement or should I add the magic number?  Should I use a DD size or not? So many of you, especially those in other countries, are baffled by the way we measure for bra patterns, and are shocked when the bra pattern size isn’t the same as their ready-to-wear bra size. Everyone at one time or another gets frustrated with bra pattern sizing. It was a real dilemma for me.


So… I developed my own method of bra sizing, called the  Bottom Cup Depth, or BCD method. I used the method to create my patterns, because it was a method that worked. Unfortunately back then,  I still named my patterns according to the ready-to-wear sizes most people in North America are familiar with. That decision to name it as RTW (ready-to-wear) sizing and not the BCD size was a decision I have regretted for almost twenty years. I confess, I wimped out. I thought no one would understand this whole new method of measuring, and therefore, no one would buy my patterns. I am determined to correct that error in judgement now. So here is the BCD method of measuring explained.

So what is the BCD measurement?

The BCD method measures the distance from the apex of the breast down to the wire line directly below it. That measurement in inches will determine your cup and frame size. Then take your Rib Cage measurement directly under your bra. That actual rib cage measurement (no magic number involved) is used for the band length.  The combination of BCD and Rib Cage is your pattern size. For example, the BCD might be 4.0 and the Rib Cage of  32. In my BCD system, you would be a 4.0/32.

The BCD size increases by 1/4″ (6 mm) per size so if you happen to make a bra cup that is too small, you simply go up to the next BCD size. So if you made a 4.0 BCD, and it was too small, you can make the 4.25 size. Isn’t that crazy easy? No more figuring out sister sizing, or moving up one band size and down one cup size or relying on ready-to-wear sizing. It is so logical, it astonishes people and they ask why this hasn’t “always” been the way bra patterns are designed.

If you already have a bra pattern that fits, you can determine the BCD from that pattern. That will make it easy to find the BCD, assuming the seam across the bra runs across the bust point. Simply measure from the seam line (not the cutting line) at the apex, straight down to the seam line below it. For most patterns, it is the deepest area of the lower cup.


You must take the BCD measurement using a bra that fits. In a perfect world, the bottom cup depth on your bra should measure the same as the bottom cup depth on your naked breast, but it often doesn’t – because of the breast density and degree of flaccidity.The nipple will drift downward as the breast loses its self-supporting ability, which means that even if your bra size does not change over the years, your BCD will still decrease as you age. Nothing stops gravity.  So it is imperative to wear a bra that fits (not a foam lined bra, or a sports bra either). The bra correctly sized, will actually appear to place the nipple in the ideal location.

Here is a chart that shows what BCD sizes correspond with “most” ready-to-wear sizes in North America and also my Pin-up Girls pattern sizes.

So why am I telling you this? Quite simply – all patterns I create from here on in, will be named as the BCD size and not typical bra sizes. The new Ruby and the Ingrid which will be released soon, are sized this way. Plus I will go back and re-vamp the other bra patterns to use this method. The custom bra-makers I have taught over the years, were trained on the BCD method and now you know about it too. It’s an idea whose time has come.

Comments (9)

  • Ruthe Ploskunyak

    August 3, 2018 at 9:35 AM

    Beverly, I had been using yours and other bra designers for awhile, and been frustrated by failing to get a good fit. I love your Craftsy classes, and feel as though I know you personally. The instruction was there all along, but my results were less than consistent or fitting. I tried your Ruby pattern, and could not be happier. It uses the BCD method as you say, and it makes all the difference in the world. Thank you for being persistent in the pursuit of quality fitting garments. You have no idea how important that is, especially to women of my age. I also appreciate you telling the truth, that gravity does kick in, and there’s no amount of wishing and fighting that will change that. I just want to look put together, and not be in pain. Your bra patterns and instructions really do make a difference!

    1. Beverly Johnson

      August 3, 2018 at 1:27 PM

      Wow, Ruth, you have officially made a good week better by these kind words. But I have a secret for you. There are at least 3 more patterns coming out that are based on Ruby!

  • JessBrat

    July 3, 2018 at 5:16 PM

    I find the BCD method frustrating. It measures only your bottom cup, and doesn’t even take the upper cup into account. When you have shallow upper cups, and full bottom cups (think of wide ovals–or in my case, spoons! haha) using your BCD will only give you half the picture. I find going around the body widthwise, as in traditional sizing, more helpful in my case, since measuring my depth is misleading 🙂 No amount of squeezing into wires or trying to redistribute tissue, nothing short of wearing a push-up, will make my upper cups fit a D cup like my bottom cups do!

  • LindaC

    July 2, 2018 at 2:34 PM

    This makes so much sense. Thanks for explaining it.

  • JenL

    July 1, 2018 at 8:30 PM

    This methods sounds clear and logical — looking forward to the new patterns too!

  • Donna

    July 1, 2018 at 4:47 PM

    Is there any way to figure out the BCD on the naked breast by supporting it by holding it?

  • Linda

    July 1, 2018 at 10:10 AM

    Bless you!

  • Michelle

    July 1, 2018 at 10:04 AM

    Thanks for sharing about this, Beverly.

  • Judi

    July 1, 2018 at 9:33 AM

    Yayyy for making sense of things. I wish the entire industry would follow your example – maybe someday they will.

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