three bras in sister sizes

Bra sister sizes UK | Discover your next best bra size!

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Every woman should know about her bra sister sizes. It could well be her next best ba size!

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Bra from M&S collection AA-K cups | See Marksandspencer.com


What are bra sister sizes?

Every bra size is surrounded by a set of bra sister sizes. These sister sizes have a different band size and a different cup size.


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However, the cup volume of these sister sizes is the same.

bra size chart with uk bra sister sizes

In this chart, you’ll see the sister sizes of 36C are 34D and 38B.


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I have 3 different bra sizes that fit me just fine.

I have one bra size I wear the most. Sometimes I go for a band size 36 instead of the 34 I usually wear. In this case, I go down a cup size to keep the same cup volume.

The cups in a 36 are also a bit wider set and I find this sometimes better for me.

Also depending on the brand and bra style, I try different sizes and actually own different sizes.

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Why should I know my bra sister size?

woman in a bra top holding a measuring tape
Regular measuring is no luxury
  • Most women can wear different bra sizes and they all fit them well. So that’s different sizes for the same woman!
  • Knowing about bra sister sizes will make shopping for bras more fun. You know what sizes to look for. And depending on the brand and bra style you may wanna choose a different bra size than you usually wear.

Because your body has changed and the bra band is either too wide or the band is too small, it’s logical to choose a different bra band.

If you want to keep the same cup volume your bra sister size is what you need.


Do I have a bra sister size?

four different smiling women in bras wearing different bra sister sizes
What’s your bra sister size?


So, every woman has a bra sister size.

Knowing your bra sister size will help you choose between different sizes if you need to. Remember that different brands and bra styles might have different fits.

I’ll give you 2 examples that’ll give you a good idea of how to deal with a bra size change.


Going up a band size | keeping the same cup size

chart uk bra sister sizes going up a band size

You wear a 36C bra. You are not happy with the band size and find it a bit too tight. You want to keep the same cup volume.

  • you choose bra size 38B (that is your bra sister size).


Going down a band size | keeping the same cup size

chart uk bra sister sizes going down a band size

You wear a 36C bra. You are not happy with the band size and find it a bit too loose. You don’t wanna change the cup size.

  • you choose bra size 34D (that is your bra sister size)

Understanding bra sister sizing is a great help in finding the right bra.


Other articles you might like

Full Guide Bra Measuring
The average bra size in the UK
Why is my bra hurting me?
UK bra size chart
Small bra chart AAA-B
Can I buy a bra without taking measurements?
The average bra size UK

Learn about your best bra size today! Check my size now

Best bra styles that suit you? 
M&S BraFit Guide