Step by step: determine your sister bra size
It is not always easy to find a well-fitting bra. Several factors can affect the level of comfort, including the material, cut and size of the bra. Even if you know your bra size, this might not be the same for all types of bra. This is where sister bra sizes come in! Read on to find out what sister bra sizes are and how to determine them.
24 March 2023 • 5 min reading time
Calculating bra cross sizes has never been so easy!
To ensure that a bra is totally comfortable, it must be the right size. Sister bra sizing is a technique that will help you find a perfectly fitting bra. Sometimes, the cup is a perfect fit, but not the underband. Or in other cases, the underband is comfortable, but the cup is too small or too big. You can use sister sizing to find out which alternative bra sizes fit you.
Here are the most common fit problems and recommended solutions for each. Once you identify the problem, you can then determine the correct sister bra size.
1. Underband too loose, but cup fits.
Go down an underband size. To ensure that the cup still fits, go up a cup size.
2. Underband too tight, but cup fits.
Go up an underband size. To ensure that the cup still fits, go down a cup size.
3. Underband fits, but cup too small.
Keep the same underband size, but go up a cup size.
4. Underband fits, but cup too big.
Keep the same underband size, but go down a cup size.
5. Underband too tight and cup too small.
Go up a bra size.
6. Underband too loose and cup too big.
Go down a bra size.
Once you have identified the problem during fitting, you can now determine the right sister size. First, find your usual size in the following table. Your sister sizes are to the left and right of your size. Depending on your fit problem, you can choose one of these sizes. If you do not know your standard bra size, we recommend using our bra size guide to work this out.
The following table provides an overview:
Sister bra sizes chart
Example 1: Your standard size is 75B. You tried on a size 75B bra – the underband is too tight, but the cup fits okay. So you should go up a number and try size 80A.
Example 2: Your standard size is 75B. You tried on a size 75B bra – the cup is too big, but the underband fits. So you should change the letter and keep the number. This means you choose size 75A.
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