Monday, May 21, 2012

Bra School: Not all D cups are the same size

From Left to Right 30D, 32D, 34D, 36D, 38D. Five different band lengths, five different cup volumes. All D Cups.
I know that bras can be confusing little minxes. When I try and explain to someone that besides their 34G bra they could also wear a 32GG they look at me with bewilderment. This post aims to give you an easy-to-understand guide to how cup sizes work.

Most people think that all D cups hold exactly the same volume of boob and then that cup size is just sewn onto different lengths of band to make the 30D, 32D, 34D etc. This is not true. 

In my world of D-K bras* you may think there are only 11 cup sizes (D, E, F, FF, G, GG, H, HH, J, JJ, K) However, there are actually SIXTEEN different cup sizes, or more accurately, cup volumes (volume refers to the amount of breast tissue a cup can hold).

In this table below I have colour co-ordinated all the D-K BRA SIZES THAT HAVE CUPS WITH THE SAME VOLUME.

The volume of each cup increases as the 'Cup Volume Number' increases. E.g. #1 is the smallest cup volume and #16 is the biggest cup volume.
You'll notice that there are six band sizes for each cup letter and as the band size increases on each cup letter the cup volume also changes. So for example, a 28D has a #1 cup volume, a 30D has a #2 cup volume, 32D has a #3 cup volume and so on.

Real Life Example
Imagine you wear a 36D; your cups fit well because they encase your breasts but your band keeps riding up. Instead of thinking of your boobs as a D cup you can think of them as being a cup volume #5. When you realize your band keeps riding up because you actually need a 32 band not a 36 then you can see that a #5 cup volume on a 32 band is actually an F cup.

What is Sister Sizing?
When people talk about sister sizing what they're referring to is all the bras with the same cup volume but on different length bands. In our chart all the bra sizes with the same cup volume number are sister sizes. For example, 28JJ, 30J, 32HH, 34H, 36GG and 38G are all sister sizes to each other because they're all cup volume #10.
 
This is the basic logic behind how cup sizes work but as always you should learn how each bra style and brand fits (we have a How This Bra Fits tab on each of our product pages). When you put on your bra be sure to look for the Five Fit Signs to make sure you're in the right size for you.

I hope this has helped (I expect I've confused a few people too). If you have any questions leave a comment below and I'll get back to you xx

*A footnote for anyone wondering why I don't use UK DD cups; it's because they are the same equivalent as US D cups so to avoid confusion I don't use the DD size.

47 comments:

  1. Replies
    1. Thanks K. Line! I hope it helps a few women to understand why they've leapt from a D cup to an F cup in one easy band move :) xx

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    2. I was wondering if the cup volume you talk about is the same as the sizing on silicone breast forms? For example, I have size#8 silicone breast forms from Amoena. So would a 38F bra ( in yellow on your chart),which is #8 cup volume, be the right bra size for size#8 breast forms?
      I wear bras size 40D with my forms which isn't on your chart.

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    3. Hi Dariana - there isn't an exact bra size for breast form numbers because it depends how the breast form sits on your body. If your 40D is comfortable and encases the breast form correctly then the sister sizes are 38E, 36F, 34FF. Hope that helps xx

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    4. Your Chart is wonderful, just one small thing, could you consider adding a few more sizes. I'm still abit confused on what I can wear as a size 42DD. Different sizes. different brands,different nationality's... I'm finally starting to enjoy wearing nice looking lingerie, companies are making larger sizes and that's a wonderful thing for someone who always had to hunt and dig for the store's one bra that might be large enough. This new change in sizes is a whole new world filled with joy for me.

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    5. I will definitely look at getting a larger size range sister size chart together as so many people have asked about it. I'm so glad you are finding joy in lingerie, that's wonderful! xx

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  2. I knew all this about band sizing, but there's no mention of DD which suddenly adds confusion to the mix. A UK DD is the same volume as a French E(going by the brand Lise Charmel. I wear a UK 32DD but I buy a 32E in Lise Charmel and they fit exactly the same) BUT a UK DD is NOT the same volume as a UK E... because I had to return a 32E UK bra because the volume was massively too big.

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    1. Try a 30E, I find that I can wear a 36DD but when I go to an E cup I have to get a 34 band :)

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    2. Think of it this way, if you're putting on a larger cup size then choose a smaller band size.

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    3. Hello MissLizzy - DD/E cups are some of the trickiest to get right because some brands fit like a UK DD cup and others fit like an E cup. You will need a DD cup in most UK brands and an E cup in European ones. It doesn't make life easy for you that there is so much discrepancy across brands in the DD/E range. You have my sympathies xx

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    4. The French and other European makes do not make a DD (or FF,GG etc) hence the E fits you the same as the UK DD, the UK E would of course be one cup bigger, the French G is UK F and H is UK FF - hope this helps!

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  3. I have to try and explain this to customers all the time, I call it cross grading ( not sure where I picked that term up from). But even then I find some high street own brand bras * coughs Marks & Spencer * don't have the same depth so give the breast a squished look. I like the way you describe it :o)

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    1. I'm glad it's helpful Kitty. I really love my customers to understand their breasts, I think it gives them a fuller bra experience. xx

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  4. The chart only goes up to band size 38...if you need band size 40 can you still apply this? For instance, your calculator says I need a 40G so I could also wear a 38GG, 36H, 34HH, or 32J right?

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    1. Hello, Yes you're totally right! Sorry I didn't make the chart bigger but you have taken the logic and used it correctly. i hope it helps. xx

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  5. And what about C cups or smaller?

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    1. The rules still apply (the chart is limited because we only deal with D-K cup bras here). So for example a 32D, 34C, 36B, 38A and 40AA are all sister sizes. Hope that helps. xx

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  6. I wonder if adding a photo of those D cup bras to show their height might help people visualize the change in volume as well- ie you show how D cups under-wires get wider as the band size goes up, but the cups also get deeper (volume being 3D and all that)
    Otherwise it's a beautiful illustration!

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    1. That's a good idea. I'm in the UK right now (a few days away from getting married!!) but I'll do it when I'm back :) xx

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  7. I am convinced that I'm a 36DD as the band stays in place and the cups fit better than a D,which I shmmoze out of, but DD's aren't listed. How do I find my cup 'volume"?
    thanks
    Reva

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    1. Hi Reva - it depends which brand you're a DD in. If it's a UK brand then you can read it as a D on this chart. If it's a US DD then you can read it as an E on this chart. Most people will tell you that a UK DD is like an E cup in North America but is isn't, it's like a D cup. I hope that helps, it's definitely confusing having so many different country systems! xx

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  8. I still don't really get it, at least how it applies to me. I usually wear a 36DD (which might be a smidge small in the cup)...I have some 38D but the cups are visibly too small (and the band is on the tightest setting, LOL). The chest measurement for the 36DD is 41" but the 38D is 42"...yet the cups are too small.

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    1. Hi Tracy - there are a few other factors to consider (sister sizing is just a guide to understanding how bra sizes are created). It's tough to compare two bras in different styles or from different brands as they all fit so differently. Even though a 34H would encase my bust I can't wear this size because the band is useless on me. It sounds as though a 36 is a good band size on you but you need a DDD cup (we list this as a 36F). The cup volume on your 36DD and 38D is approximately the same and the cups are too small on both so you need a larger cup on a snug band. We can always help you out with a size consultation too http://www.butterflycollection.ca/free-bra-size-consultation/ I hope that helps! xx

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  9. Shouldn't it be that one band size = 2 cups sizes? I was thinking about this since band sizes are measured every two inches (32,34,36...) but cup size is determined by one inch difference in overbust measure.

    So I've now measured myself with +4 to be 38C (underbust 34+4, overbust 41), if I go toward my true band size (34), my overbust difference is 7 inches bigger which would make me a 34FF. Yet based on your chart sister sizes for 38C (cup volume #5) would be 36D and 34E, putting me into a cup too small.

    I'm confused!

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  10. Hello! You're comparing two different measuring methods (they have different band starting points). Adding inches to your underbust measurement puts you in a bra that doesn't fit so you're comparing two different methods, that's why you're getting different results.

    Your 34FF has the same cup volume as a 36F and a 38E. When you distort the starting band size (by adding pointless inches) the sister sizing will just give you more wrong results because you're starting in the wrong result, that's why we don't add inches. Hope that helps xx

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  11. Does the sister sizing mean you can go to a different size close to your preferred size?

    For example, there is a bra garment I would dearly love to purchase but they don't go above a (UK) F cup. I'm a G or GG (depending on brand) with a 32 band. What size could I go to then using the "sister sizing"?

    Many thanks.

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    1. Such a good question. Sister sizing sounds like you should be able to wear any of the sizes that are 'sister sizes', but the term really just means "bra sizes that share approximately the same cup volume."

      You could buy a 34 or 36F and get the same cup volume as your 32 G/GG but other parts of the bra would change, namely the band would be too loose.

      If you really want the piece of lingerie that only comes in an F cup then you should set aside some budget to have the bra tailored so that the band is tight enough and the gore lies flat.

      Sister sizing is really useful to explain to women wearing a 38DD that they can get the same volume from a 32G but better band support.

      Hope all that helps! xx

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  12. Hi myladyswardrobe,

    I work in a retail store (unfortunately I haven't yet been trained how to do bra fittings), and one of the girls I work with is quite petite with a reasonable bust. She tells me that she usually buys her bras in her next sister size up and then gets a tailor/someone who's good at sewing to take the band in a little at the back to fit her band size. There are a few tutorials on it on the internet (I have a similar problem to her in that my bra size is quite difficult to find where I live), my suggestion would be to take a look at some of them. Generally they advise not to use bras that are too big in the band, as the piece in between the cups tends to be a bit bigger with larger sister sizes.

    If you were a 34G, I'm guessing your next sister size up would be a 36FF, then a 38F, etc. If you're closer to a 34GG, it'd be 36G, 38FF and 40F. Hope this helps a little!

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    1. That's a great point about the online tutorials, I know some of the small back, full bust bloggers have used those. Thanks for sharing the idea Jayne! xx

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  13. Okay, I am confused. Under this theory when I lose weight shouldn't I be able to go down cup sizes as well as band sizes? But I don't. No matter what band size I am wearing I always have to have a U.S. DDD cup. My band size does change when I lose weight though.

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    1. Hello - I know it can be a bit confusing but when you come down a band size and your cup doesn't change letter you have actually come down a band size. A 32DDD cup has a smaller cup than a 36DDD. So when you lose weight your band and cup are both getting smaller. If you were only losing back sizes but not cup sizes you would see an increase in your cup letter and a decrease in your band size. For example if you were a 36DDD and you lost body weight but not boob size you would come down to a 34FF, a 32G, a 30GG etc.

      Hope that helps. xx

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  14. Such a helpful post and reflects the conversations we have with our customers too. Also shows just how much confusion there still is out there! It's great that people can use on-line forums/blogs to ask the questions that they might not feel confident enough to ask a shop assistant in person.

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  15. What a great post. I do see the different size D's when I look at my 30D to 44D bras, all laid out, it's an amazing site to see.

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    1. It's such a great way to see the band to cup ratio at work. There are 7 cup sizes between your 30 and 40 D cups so you can easily see what a difference the band makes! xx

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  16. Am buying a bra on site and they have stated the sizes in A B C D and so on but am 34D so i don't know which size to choose from their size chart.Can you help me out here?Thank You

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    1. Hi - If you're a 34D then ordering a 34D should be fine but it depends on the particular bra. Are you ordering from our site? If so then you can email support@butterflycollection.ca otherwise it's a good idea to contact the site you're ordering from and ask how the bra you want fits. xx

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  17. I think I am still confused:

    If I am a 40 DD, then would I get a 38F or 36 G? I don't see the 40 band sizes with some of these brands.

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    1. You're right, a 40DD would translate as a 38F, 36FF (which is a 36G in bras made by an American manufacturer) 34G, 32GG etc. No single brand carries all the sizes that are available. A 40DD (or 40E in UK brands) is considered plus size so brands that don't make plus size bands won't carry this size. xx

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  18. Hi,

    I am a little confused. I have a nursing bra that is a 36 DDD. Can you tell me the sister sizes??

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    1. We find that most DDD cups fit like an F cup. If the cups on your 36DDD fit you then your sister sizes are 34FF, 32G and 38E, 40D. Ideally you want to wear a bra band as close to the measurement around your torso. E.g. If you measure 33 around your torso (where you bra band lies) then you can wear a 34FF or a 32G depending on how snug you want your band. xx

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    2. Thank you!!! I am printing this out!! Where do you recommend we find bigger bra cups? Having a hard time finding the bigger cups.

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    3. Our store only carries bigger cup bras, this is the blog for our store. www.butterflycollection.ca If you're in Canada or the US then we have free shipping options available every day xx

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  19. Hi, I have a question. I have 34.5" band and 42.5" bust. I have been sized at 34DDD, 34FF, and 34G, all by professionals, just at different stores. What the hell is my base size? I have never found a bra that fits comfortably, and I'm only 22 years old. Help!?

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    1. Hi Ally - Based purely on your measurements I would put you at a 34G. However, things like your height and breast shape affect size and fit so it's worth using our Free Size Consultation to get a more in depth fit conversation with one of our fitters http://www.butterflycollection.ca/free-bra-size-consultation/

      If you've tried a 34G then it's worth letting the fitter know what was uncomfortable about the style (and brand of bra) you tried in a 34G. One thing for sure, in your size range there are lots of bra shapes so the chances are very high that you can find a comfortable fit once you narrow down what features you need in a bra xx

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  20. It still seems to make no sense.

    According to your bra size calculator the 38D above has an underbust of 38 and an over bust measure of 42 (that's what makes a 38D per the calculator). That's a 4" difference. In this case a 4" difference makes a D cup?

    But the 30D with an underbust of 30 and an overbust of 36 is a 6" differential. In this case a 6" difference makes a D cup.

    If I enter a 38 underbust with a 44 overbust (6" difference) then I get a 38F.

    Shouldn't a 6" differential produce a more voluminous cup than a 4" differential? The projection must be less with a 4" difference so why more volume in the cup? According to your picture above, the breast diameter got significantly wider with each size, but yet the proportional projection is less. It does not follow that the cup should have more volume.

    I think the overbust measurement is meaningless as nothing is fitting around that part of the body. Only the band matters circumferentially speaking. The breast mound itself should be measured for diameter and measure from the breast tissue at the side to where it ends near centre front. That should be breast volume.

    A sister size bra would have a longer band, the straps and cups/bust apexes would be further apart and technically should still not fit, especially since the band is the most important part. I think once the band size is correct, you should not deviate from it as it is probably 80% of the bra's support.

    I would like to see the data that shows breast diameter changing as the underbust changes. Many times these two are unrelated. ie: a woman with a wide back and small breasts, or a woman with a small back and large breasts - the current system would have them in the same size bra.

    I know that bra manufacturers created sister sizing but it has little to do with women's actual sizes and more to do with convenience in bra grading. I'm not sure it's built on any kind of human data.

    This problem will always exist until we measure the actual breast mound as a separate component from the band size. While we are still relating band to cup size, the issue will keep confounding.

    Thanks for the great discussion - there is growing recognition that the entire system is flawed.

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  21. I'm not sure if you entered the 30 ribcage and 36 overbust measurements into our calculator but you would have got a result of 30F standard, 32E loose and 28FF tight. A 6 inch difference between the apex and the underbust measurements would rarely be a D cup (however, it can be if the breast root is wide and the projection is shallow). No calculator or single bra rule will ever apply to every woman's breasts. In this blog you'll find article about all the unique features that affect cup size from height and ribcage shapes to breast root widths and heights.

    The sister sizing guide is a good starting place for understanding that as the band gets shorter the relationship of band length to cup volume changes (the same cubic volume of breasts on varying widths of band equate to different cup letter/band number combinations).

    I know it's frustrating that there isn't a single rule you can follow to explain all breast fits. Understanding how the manufacturers create bras then narrowing down the features that are relevant to your bust is our primary objective.

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