Sister Sizes Explained

What is a Sister Size?

If you've been in-store for a fitting and spoken to one our professionally trained fit experts, you may already be aware that you actually have two bra sizes. If you haven't, we're here to let you in on a little (big) secret.

Bra sizing is a kind of magic, where one bra size can have many sizes.

Sister sizes are groups of bra-size equivalents that are related by cup volume. Where your specific bra size might have a number or related sizes. This means that if you can't find your favourite style in your size, you might be able to choose your sister size.

How do you know, when to size up or size down for a sister size

You don't need to wait to use this trick to find a bra in a particular size - if your fave has sold out.

If you are happy with the cup size that you have and the way that it fits. But the band size feels a little firm - you can go up a back size to have a bit more room - and use the sister size to keep the same size cup! For example, if you fit a 12D in the cup- but feel like the band might be a bit too tight you could move up to a size 14C to get a bit more room in the band and keep the same cup.

Alternatively, if you feel like the band is a little loose but the cup fits, and you would like a more firm fit. Size down in the back, just remember to go up in the cup size to get the same size cup. For example if you are wearing a size 16C, but feel like the band is a little loose you can go down a back size to a 14 and up a cup size to a D cup.

Rule of Thumb

If you go up a band size, then you go down a cup size.

Or...

If you go up a cup size, then you go down a band size.

Sister Size Chart

Using the table below find your size - all sizes on the same row are your sister size. For example, a 12D has a sister size of a 10DD, 14C, 16B or 18A.

8A 10AA - - - - - - - -
8B 10A 12AA - - - - - - -
8C 10B 12A 14AA - - - - - -
8D 10C 12B 14A 16AA - - - - -
8DD 10D 12C 14B 16A 18AA - - - -
8E 10DD 12D 14C 16B 18A - - - -
8F 10E 12DD 14D 16C 18B - - - -
8FF 10F 12E 14DD 16D 18C 20B - - -
8G 10FF 12F 14E 16DD 18D 20C 22B - -
8H 10G 12FF 14F 16E 18DD 20D 22C - -
8I 10H 12G 14FF 16F 18E 20DD 22D 24C -
8J 10I 12H 14G 16FF 18F 20E 22DD 24D -
- 10J 12I 14H 16G 18FF 20F 22E 24DD 26D
- - 12J 14I 16H 18G 20FF 22F 24E 26DD
- - - 14J 16I 18H 20G 22F 24F 26E
- - - - 16J 18I 20H 22G 24FF 26F
- - - - - 18J 20I 22H 24G 26FF
- - - - - - 20J 22I 24H 26G

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Signs it’s time for a bra fitting

We recommend that you get fitted once every 12 months. However, if you notice your body is changing you should get professionally fitted, regardless of how recently you were fitted. A woman's body can change due to puberty, pregnancy and due to fluctuations in weight. Wearing the correct bra size promotes good breast health, it’s important to keep an eye on any changes in breast size. 

Guide to buying her first bra

If you think it’s time to start shopping for your daughter's first bra, we’ve got you covered. We recommend popping into your local Bendon store for a professional fitting. If you’re interested in more information, check out our guide The First Bra for Beginners: How to buy your daughter her first bra. 

What happens at a fitting

A bra fitting is a super quick way to find out your bra size. One of our lovely retail team members will measure you, have a quick chat about your favourite bra styles and then complete a fit check. If you want to know more about what happens at a bra fitting, check out our guide. 

Fit finder tool

Gone are the days of wearing the wrong-sized bra! Take our fit finder quiz to find your perfect fit.