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| From Left to Right 30D, 32D, 34D, 36D, 38D. Five different band lengths, five different cup volumes. All D Cups. |
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.
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| 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. |
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.
This post is genius!
ReplyDeleteThanks 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
DeleteI 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?
DeleteI wear bras size 40D with my forms which isn't on your chart.
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
DeleteI 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.
ReplyDeleteTry 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 :)
DeleteThink of it this way, if you're putting on a larger cup size then choose a smaller band size.
DeleteHello 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
DeleteThe 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!
DeleteI 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)
ReplyDeleteI'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
DeleteThe 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?
ReplyDeleteHello, 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
DeleteAnd what about C cups or smaller?
ReplyDeleteThe 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
DeleteI 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)
ReplyDeleteOtherwise it's a beautiful illustration!
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
DeleteI 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"?
ReplyDeletethanks
Reva
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
DeleteI 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.
ReplyDeleteHi 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
DeleteShouldn'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.
ReplyDeleteSo 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!
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.
ReplyDeleteYour 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
Does the sister sizing mean you can go to a different size close to your preferred size?
ReplyDeleteFor 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.
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."
DeleteYou 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
Hi myladyswardrobe,
ReplyDeleteI 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!
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
DeleteOkay, 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.
ReplyDeleteHello - 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.
DeleteHope that helps. xx
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.
ReplyDeleteTotally agreed! xx
DeleteWhat 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.
ReplyDeleteIt'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
DeleteAm 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
ReplyDeleteHi - 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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