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Bra sister sizes: do I have one?

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

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different women different bra sizes
You too might fit 2 or 3 different bra sizes


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 number cup size. However, the cup volume of the sister sizes is the same.

chart with example of bra sister sizes
Example of the sister bra sizes of 36C

Especially if you’re in between two possible band sizes you’ll surely have a bra sister size you might wanna try and buy sometimes.

I myself 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.


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The cups in a 36 are also a bit wider set and I find this sometimes better for me. Depending on the brand and bra style I try different sizes and actually own different sizes.

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Why should I know about bra sister sizing?

woman in a bra top holding a measuring tape
Regular measuring of your bra sizes 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 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 of the fact that 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?

Every woman has a bra sister size.

I think it’s a must-know when shopping for a bra. 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.



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Going up a band size | you want to keep the same cup size

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

  • you choose bra size 38B (that is your bra sister size).
bra sister sizing example
A 36C and a 38B have the same cup volume


Going down a band size | you want to keep the same cup 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)
bra sister sizing example
A 36C and a 34D have the same cup volume

Understanding bra sister sizing is a great help in finding the right bra. Read all our topics on bra sizing in our measure guide »


Other articles you might like

How to measure my bra size at home?
About the average bra size in the UK
UK bra size chart and how to use it
Why is my bra hurting me?


Check your size in my bra calculator
of visit M&S for advise and size chart

measure tape bra size uk

Marks & Spencer | Find your Perfect Fit
UK | US | CA | IE | ES | FR | AU
select your shop/country

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