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What are Sister Sizes?

A guide to sister sizes

Belle Lingerie18 May 2021

Sister Sizes

The term ‘sister size’ is a technical term often used in the lingerie and bra industry and we bet you’ve heard it a lot but don’t really know what it means. Understanding how it works and what it means will definitely help you in the long run, to find the perfect new bra. Getting the right fit of bra can be so tricky, especially with so many types and brands out there. Trust us, we know how many are out there since we sell almost 80 different lingerie brands and almost 4,000 different bras! So, sister sizing is there to help and to give you some wiggle room when it comes to your bra size. Let us explain further…


How Sister Sizing Works

To help you understand sister sizing, let’s look at sizing overall. You can look at our full sizing guide for all the details but for a quick summary, here in the UK, the cup size is represented by letters (A – JJ) and the band size is in numbers (32 – 50). Please bear in mind that different countries and parts of the world have different sizes, you can check our international size convertor if you are from outside of the UK.

Your band size and your cup are relative, so cup sizes are not the same size if you are not the same back size. For example, if you are a 32D, that cup volume is going to be different to someone who is a 36D. The capacity of a cup increases with the band size. And the fact that band size is based on the inches just under your bust, your cup size will always be determined by your personal measurements.


What is Sister Sizing?

Now you have an idea of how sizing works, onto why you actually clicked on this blog. Sister sizing is an alternative number and letter to your current size but there will be a very slight difference in overall size and fit. You can size up once or down once and these will be your sister sizes. The cup letter may change but the actual capacity of the cup won’t differ.

Example of sister sizing – If you are a 34D your sister could either be a 32DD if you size down or a 36Cif you size up.

You will find your sizes below. If you find your normal size and then look at the one to the right and the one to the left.


Should I Sister Size Up or Down?

Both ways will be quite similar but depending on your boobs you might want to lean towards up or down. If your bra is on the tightest hook on your back fastening, you might want to consider your sister size down. However, if you’re on the loosest hook, we would recommend leaning toward going for your sister size up. But as we said there isn’t too much difference so you can always try both.


Why Use Sister Sizes

Sister sizing can come in handy in a few instances. Firstly, if you are buying a bra from a new shop or brand you may find your normal size doesn’t quite fit. In this instance, we would recommend trying your sister sizes as they are not too different but might be different enough to find you that perfect fit. Sister sizes give you the opportunity to find flawless fits in various styles and brands. Also, if you find a bra you really like the look of but unfortunately Belle Lingerie has not got your size, why not try your sister size? You could grab yourself a bargain at Belle Lingerie if we have sold out of your normal size in our special offers but not in your sister sizes! You will find your sister sizes will come in handy over time, now you know all about them.

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