Everything to Know About Bra Sister Sizes

Getty | harpazo_hope

For me, shopping for a new bra and underwear is, admittedly, a bit of a rarity. Once I find a bra that is comfortable and functional, I use it for years on end. While the main reason behind my infrequent bra shopping sprees is the fact that I only need a couple versatile bras to get the job done, another factor is finding the perfect bra size and bra sister size. It can be tricky to find the right lingerie size when you have to take band width, cup size, and breast size all into account. Additionally, our bodies fluctuate so often, and different brands have different sizing charts and definitions. All in all, it can just make the task seem more complicated than it's worth. But if you can believe it, bra sister size charts help make the fit process a little bit easier.

Unlike the traditional bra sizes that you may be familiar with, like 28C or 42A, sister sizes take into account volume. Basically, they are sizing groups, equivalent to bra sizes, that are based on cup volume. And the volume of cup size varies with the band width. It's easy to calculate your sister bra size. If your band is too tight, go up a band size but go down a cup size. Do the same calculation in reverse if your band is too loose: go down a band size, but go up a cup size.

What Is a Bra Sister Size?

Sometimes you may find a comfortable band width with a certain bra size, but the cups are a bit too tight. If you go up a traditional bra size to find a better-fitting cup, you might also experience a looser band. That's where bra sister sizes are helpful, because if you find the sister size to your established bra size, you may find a better-fitting cup — but you can still maintain the perfect band without it feeling too loose.

According to bra sister size rules, if your band fits but your cups don't, adjust the cup size. If it's too small, go a size up, and if it's too big, size down. However, if your cup fits but your band does not, then adjust both band and cup size. If you need to go up in band, go down in cup size, and vice versa. If neither your band nor your cup size fits, focus on adjusting the band size to your comfort and liking, and the cup size should naturally adjust.

Bra Sister Size Chart
Getty | harpazo_hope

Bra Sister Size Chart

We've put each bra size and its coinciding sister sizes in this bra sister size chart. So, next time you go bra shopping, make sure to take into account your bra sister size so that you choose the best bra for you.

30 32 34 36 38 40 42 44 46 48
30B 32A 34AA
30C 32B 34A
30C½ 32B½ 34A½
30D 32C 34B 36A
30D½ 32C½ 34B½ 36A½
30E (DD) 32D 34C 36B 38A
30E½ 32D½ 34C½ 36B½ 38A½
30F (DDD) 32E (DD) 34D 36C 38B 40A
32E½ 34D½ 36C½ 38B½ 40A½
30G 32F (DDD) 34E (DD) 36D 38C 40B
32G (DDDD) 34F (DD) 36E (DD) 38D 40C 42B
32H 34G (DDDD) 36F (DDD) 38E (DD) 40D 42C 44B
34H 36G (DDDD) 38F (DDD) 40E (DD) 42D 44C 46B
36H 38G (DDDD) 40F (DDD) 42E (DD) 44D 46C 48B
38H 40G (DDDD) 42F (DDD) 44E (DD) 46D 48C
38I 40H 42G (DDDD) 44F (DDD) 46E (DD) 48D