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If you've found that finding your right bra size is a frustrating process, there are some sizing hacks that can make finding your perfect fit much easier. One of the most effective of these is the use of “Bra Sister Sizes”. You may be unaware that every bra size has several "Sister Sizes"- these are sizes which have an equivalent cup capacity, despite the letter of the cup size being different. Knowing your sister sizes can help you find your best fit when buying bras that run smaller or larger than normal.

It’s a common misconception that the larger the cup size, the larger the bra, no matter what the band size (i.e. a 32F is larger than a 36B, a 34C is larger than a 38A, etc). However, this is not the case. During the bra manufacturing process the same exact bra cup may be paired with different band lengths to create multiple bra sizes. For example, the same exact cup is used to make 38A, 36B, 34C, 32D, AND 32DD bras! The reason for this is that within each cup size (A, B, C, D, DD, etc), as the band size increases, the cup size also slightly increases even though the letter does not. For example, a 34B bra and 36B bra will not only have different lengths, but the capacity of the cups will also differ. Once you understand that there are equivalent “sister sizes” to your own bra size, it can help you solve any bra fitting issues you may have.

Bra Sister Size Size Comparison Chart:

Common Fit Problems and How to Solve them Using Sister Sizes:

To change your Band Size and keep the same Cup capacity, remember that the 36C with cups that fit you (for example) has the same cup capacity as the 34D with the smaller band size and the same Cup capacity as a 38B that has a larger band size .Getting your best fit will require both the band size AND cup size to change. For another example, if you are wearing a 34B bra and the band is tight but the cups fits well, instead of going up to a 36B, you should choose your equivalent sister size, 36A.

If you both the band and the cup are a bit loose, the band should go down and the cup capacity should go down too. Remember that with a smaller band bra, the same Letter cup size is going to be smaller. For example, if you are wearing a 34B that is too loose in both the band and the cup, try a 32B. It's a smaller bra, so the same Bcup in a 32 is smaller than a Bcup in a 34. If you have a 34B that is too Tight in both band and cup, get a bigger band, and remember that in a bigger bra the same Cup Letter is bigger too. So a 36B is bigger in band and cup. By knowing your correct bra size, as well as what your sister sizes are, you will be able to choose the best option to give you a perfect fit. ! For more sizing help, international size conversions, or to try our new mobile sizing app, please go to our Sizing Help page by clicking here.