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answers to your frequently asked bra sister sizing questions

We know how challenging bra shopping can be, especially when it comes to bra sister sizing. While some of us may never use sister sizing, many of us will at some point. Bra sister sizing is useful when you’re shopping for bras from a brand that fits differently from the brands you usually buy. In fact, in some cases your bra sister size might be a better fit than your regular bra size. This is why it’s so important to understand what bra sister sizing is and when you might need to use it.

We’re passionate about helping you find bras that fit well and feel good, so we’ve created two simple charts to make bra sister size conversions as easy as possible. You can find our bra sister size conversion chart here and our US to UK bra size conversion chart here. We receive a lot of questions about bra sister sizing, so we’ve compiled some of the questions and answered them for you below. We hope they help you find the perfect fit!

What is bra sister sizing?

Bra sister sizing is a method of calculating an alternate bra size with the closest cup volume to your regular bra size in the next band size up or down.

When calculated correctly, your bra sister size should closely match the cup volume of your regular bra size.

For example, with bra sister sizing, a 32D, 34C, and 36B are all closely related in terms of cup volume, but the band size varies with each. If you’re typically a 34C, a 32D would be your sister size with a smaller band size and a 36B would be your sister size with a bigger band size.

bra sister size

What is the difference between my regular bra size and my sister bra size?

With sister sizing, the cup volume will be relatively the same, so the biggest difference between your regular bra size and your bra sister size is the fit of the band. Since 80% of your bra’s support comes from the bra band, you’ll want to double check the fit of the band in your sister size to make sure it fits well.

bra sister sizing

When would I use sister sizing?

In most cases, you would use sister sizing when the cups fit well, but the band size of your regular bra size feels too big or too loose. With sister sizing, you can adjust for the fit of the band without compromising room in the cups.

bra sister size conversion chart

How can I find my bra sister size?

You can find your bra sister size with our conversion chart here.

uk bra sister size

I want to buy bras from a brand that uses UK sizing but I only know my US bra size.

If you’re shopping for brands that use UK sizing, check out our US to UK bra size conversion chart here.

find uk bra size

I’m new to sister sizing. Is there anything else I should know?

When it comes to sister sizing, be sure to double check the fit of the cups and band. You want a band that fits snugly, but isn’t too tight or too loose. Also, be sure to scoop all of your breast tissue into the cups so the side underwire sits behind where your breast tissue starts. Many bra fitters call this the “swoop and scoop”!

Lastly, try not to worry about the size on the tag. No one will see it but you. If wearing a size different than your regular bra size makes you uncomfortable, it’s completely ok to cut the inner bra tags out.

More than anything, it’s most important that you find a bra that fits well and feels good. If your sister size provides the best fit, wear it with the same confidence as you would with any other bra in your lingerie wardrobe!


Related: Find Your Bra Sister Size With Our Simple Chart


We Highly Recommend

Whether you’re shopping for new everyday bras or lingerie for a special occasion, it’s always a good idea to seek out a second opinion. We know how hard it is to find bras that fit well and feel good, especially when you’re doing it on your own. If you’ve ever felt unsure about your bra size or you just don’t know where to go to find good bras, it’s time to let a bra fitter help.

Many specialty lingerie boutiques offer bra fittings. Their expert bra fitters will take the pain and frustration out of bra shopping and do all the work for you. Even better, their product knowledge can save you time and money. Plus, they know where all of the best bras are hiding.

If you’ve struggled with finding bras in the right size, it’s time to make a change. Visit our specialty store locator to find a store near you and schedule an appointment.

Happy bra shopping!


Featured Lingerie:
Parfait Ellie Unlined Wire Bra P5082Parfait Ellie Hipster P5085 in Pewter
Jeanie Plunge Molded Bra 4801 in Panther Print, Nude, Black, Navy Blue

Published by

Katie Donnelly

Katie Donnelly is a full-time freelance writer, content manager, and founder of Katie Rose Creative. An experienced bra fitter, Katie has helped hundreds of people shop for lingerie. Her favorite bra is the Sandrine Plunge Longline Bra.

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