You may or may not have heard of this, but the sizes that surround your current bra size are called your sister bra sizes. It’s good to know what they are and how they differ from your correct bra size. This way, when you try on a bra that is not running true to size, you can quickly figure out the bra size that will probably fit you. And, if you feel you need to make a size change due to one or more of the factors that can cause your breast size to change, you again can quickly figure out your new bra size.

Let’s assume your bra size is 36C. Here are your sister bra sizes in your bra size neighborhood.

Going horizontally, you will change both your band and cup size. Want a bra both one size smaller in the cup and band? Go to a 34C. Want a bra both one size larger in the cup and band? Go to a 38C.

34B36B 38B
34C ← 36C →38C
34D 36D 38D

Going vertically from your base bra size will give you just a cup size change. Want a smaller cup? Go up to the 36B. Want a larger cup? Go down to the 36D.

34B36B 38B
34C ↑ 36C ↓38C
34D 36D 38D


Going diagonally will change your band size while keeping your cup size. Does this not seem right? Well, that’s because when you go up a band size, your cup size needs to come down by a size to maintain the same cup volume you had with the smaller band. Want a smaller band? Go left and down to the 34D. Want a larger band? Go right and up to a 38B.

34B36B 38B
34C   36C  38C
34D 36D 38D

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