Sister Sizing: The Secret to a Perfect Bra Fitting By Zivame


For 50% of the world’s population, there is one piece of garment that defines power like no other – the bra. You wear it to feel comfortable and powerful. A good bra is enough to transform a woman from a meek girl next door to the ultimate boss lady! But, as much as women love it, getting the right fit is a challenge in itself.

So, if you are wearing one right now (unless you are at home and haven’t seen them in ages!), there is a good chance that the fit is not correct. Almost 80% of women do not always get the right size or even know what the right sister sizing for them is!

But, let’s be clear on one thing, whether to wear a bra or not is up to you and it’s perfectly fine to go either way (much love to bralessness!) but wearing the wrong size and fit is NOT OK. Wrong sizes and incorrect fits can cause more drama in your life than you probably want from a pair of bras.

So, to save you from the horrors of haggling with the fitting lady at your bra store, here’s everything you need to know about bra sizing, sister sizing and why you should get the right fit. Happy reading!

Sister Sizing – Breaking Bra Stereotypes

Every woman who has ever bought herself a bra knows the frustration when the same cup and a band size of a new bra don’t fit the same way as other bras. Bra sizing is quite different from any other ready-made clothing for various reasons – breast shape being one of them. In this context, sister sizing is the saving grace! So, what are sister sizes? And why should you opt for these instead of absolute bra size? Read on.

What Is The Sister Size For A Bra?

Sister sizing for a bra is a group of bra sizes that fall within the same group based on the cup volume! Confused? Well, read on to understand this better. If you know anything about buying bras, you probably already know about two parameters (a number and a letter) that make a bra size – the band size and the cup size. The band size is pretty straightforward, the size of the band that goes around your chest. The cup size denotes the volume of the cup and is the measure of how much breast tissue it holds. This cup volume changes with band sizes.

The general rule of thumb is that cup volume and band size are inversely proportional. When you go up a band size, you must lower the cup size by the same number. So, a 34C is similar to 36B, and a 38 B is comparable to a 36 C. Here’s an even simpler breakdown for sister sizing.

  • When sizing down: Choose one size smaller than your usual bra size (36 becomes 34) and go one letter higher (B becomes C). So, if you usually wear a 36B while sizing down, it should be 34C.
  • When sizing up: Choose one size bigger than your usual bra size (36 becomes 38) and go one letter lower (B becomes A). So, if you usually wear a 36B while sizing up, it should be 38A. 

Knowing the sister sizing for your bra from your favorite brand becomes a Hail Mary if you like a particular style and the shop doesn’t have the right fit. Any good bra retailer will list down their typical sister size guide along with the product description so that you do not have to work too hard to calculate your sizing. However, knowing how math works is always a good thing!

Size Up or Size Down? Making the Right Choice!

Yes, as you guessed, there’s more to finding the correct bra fit than just knowing the formula. There is a right way of deciding whether you should size up or size down. Answer the question below, and depending on the three possible responses, decide for yourself.

Which Hook Do You Usually Wear Your Bra?

Answer 1: On the first hook.

Size up. If you usually wear the bra on the loosest hook, it is best to size up when choosing sister sizes.

Answer 2: On the last hook.

Size down. If you wear your bra on the tightest hook, size down for the best sister size.

Answer 3: On the middle hook.

Either one of them works equally well. Depending on what is available in the store, you are free to size up or size down!

Summing Up

Choosing the right bra size is one of the most critical decisions you make as a woman. Considering a woman spends up to 10 hours wearing one every day, you must choose the right companion for yourself!

Shop now from our exclusive range of everyday T-shirt bras, padded and non-padded bras, wired and non-wired bras, bras with full, medium and low coverage, and more. We also have strapless bras, backless bras, bralettes, push-up bras and minimizer bras in different designs to suit every woman’s needs. Plus, don’t forget to look up some stylish panties, like hipsters, tummy-tuckers, shaper panties, seamless panties, and panties with low, medium and full coverage!