|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.
|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.