By: Courtney Rappold

Bra shopping involves a lot of trial and error, even if you know your correct bra size. Not every bra you try on in that size will be a proper fit and chances are you will need to try on a bunch of bras until you find "the one". Your "regular bra size" is more of a guide to helping you find the perfect fit.

  This is when bra sister sizing comes into play, but what exactly is sister sizing? Sister bra sizing is an alternate bra size with the closest cup volume to your regular bra size in the next band size up or down. For example the same exact cup size is used to make 38B, 36C, 34D, AND 32DD bras, making them all sister sizes!

    From time to time, you probably have noticed different brands and styles of bras fit you differently despite having the same cup letter and band number on the tag. Even the fabric type and construction of the bra play a huge role in whether it fits or not. Because every lingerie brand uses their own measuring systems, you may need to size up or down in the band or cup (using sister sizing) to get the right fit.

Calculating your normal bra size can be hassle, luckily finding your sister size (once you know your regular size of course) should be a piece of cake! Thanks to our friends at Parfait Lingerie, here is step by step instructions on how to find your sister sizes!

1. Locate your bra size on the chart.

2. The bra size directly above your bra size is your sister size with a smaller band and bigger cup.

3. The bra size directly below your bra size is your sister size with a bigger band and smaller cup.

For example, if you normally wear a 34D in bras, your sister bra sizes are 32DD and 36C.

Sizing chart is provided by Parfait Lingeire and reflects sizes in UK sizing

 In most cases, you will use sister sizing when the cups fit well, but the band size of your regular bra size feels too big or too loose. Since the majority of a bra’s support comes from the band – and not the straps and cups like we often like to think, you want a snug and supportive band that stays in place for the best fit. Using your sister sizes can sometimes help to ensure you have a proper fitting band.

    Because not every lingerie brand or style fits the same, you might use your sister size when looking for a particular style. Every brand uses its own measuring systems, and even within the same brand, you may find particular styles run smaller or larger. For example, a balconette bra may run small in the cups, while a full cup bra - which generally has more coverage, may run larger in the cups. You might even be surprised to find that some styles fit better in your sister size then your normal bra size.

  While sister sizing does open a window of opportunity for more sizes and choices, keep in mind not every bra or style may be compatible with your sister size or body type and that's perfectly normal! If you need help with finding