Press "Enter" to skip to content

Bra Sister Sizes To The Rescue – Sisterhood Of Bras

Have you ever faced a situation where you just couldn’t find the right fit bra or that your size is not available? If yes, bra sister sizes will be at your rescue. You must be wondering what a sister size is & how can you find yours. To your surprise, every bra has several sister sizes. To be honest, even I was surprised to know that something like this exists. So, without further ado, let’s start with the blog.

What Is a Sister Size of Bra? 

Sister bra sizes are alternate sizes where the cup volume stays the same even though the band size and cup letter change. The reason is that cup sizes aren’t consistent by letter, they’re consistent by band size. Larger the band size, the larger the cup. Therefore, the cup of 34B is the same as 32C or 36A. Knowing your sister size will help you in finding the right-sized bra for you. 

One common misconception that goes around is no matter the band size, a larger cup means a larger bra size. However, one cup size is paired with multiple band sizes to make multiple bra sizes. E.g., the sister size of 36A will be 34B. Understanding sister size will help you find your comfort fit.

How To Find The Sister Size of Your Bra?

Finding the right bra size is just a game of ratios. If you excelled in the band-to-cup ratio, you’ll likely excel in the bra fitting issues. The general rule is if you go up a band size, you should lower the cup size i.e., a 34C is bra size equivalent to 36B. Here’s a breakdown for you.

Size down: Go one size lower than your actual band size & go a letter higher than your cup size. So, if you’re a 36B, your sister size will be 34C.

Size up: Go one size up your actual band size & go a letter lower than your cup size. So, if you’re a 36B, your sister size will be 38A.

Here’s a bra sister size chart to help you slip into the perfect one!

Sister Size Table
Sister Size Table

Which problems do sister sizes solve?

Until now, all you knew about cup size was that a 34C fits me and it was the end of the story! You could have never imagined yourself buying a bigger size unless you had lost or gained weight. But thanks to the sister sizing, it is an amazing way of finding the perfect fit that you have been looking for! Sister size will help you pick a bra size that fits your precisely and promises to be your favourite.

Here is what sister sizes solve for you.

The band fits, but the cups don’t

If your band fits perfectly, but the cups are either too big or too small. You’ll require to change the cup size but not the band size. E.g., If you’re a 34B & its cups are tight, your ideal sister size would be 34C.

The cups fit, but the band doesn’t

If the cups of your bra fit properly but the band size is either too small or too big you’ll require to change both to get a perfect fit. E.g., If you wear 40A and the band is loose but the cup fits then you’ll band down from 40 to 38 & the bra size equivalent of 40A will be 38A.

Neither your cup nor band fits

If your problem is that neither the band nor the cup fits you. The band will change but the cup size will likely stay the same. So, if 34B is small for you both in terms of band & cup, you should get a 36B as it would give you a larger band as well as the cup.

What are you waiting for sister? Spread the word & go on a bra shopping spree with your besties. If you’re confused about your size you can refer to our bra size calculator for a better experience. 


Q1. What is the sister size of a 34 B bra?

A1. 36A and 32C will likely be your ideal sister size.

Q2. Where can I find a bra size equivalent chart?

A2. The bra size equivalent chart gives you all the information about your sister sizes. You can refer to the above blog for more information.

Q3. Where can I find the sister bra size chart for the 40 A bra size?

A3. The ideal sister size of 40A will be 38B. You can refer to the above blog for more information.