Sister sizing made easy

Sister sister sister

When it comes to sister sizing across bras it can be confusing how or why it works. Sister sizing works because it maintains a balance between the band size and the cup volume. The easiest way to think about it all is to imagine a squishy rectangle, if you squash the back and sides in (ie make the band decrease) the rectangle will push out at the front (ie increase the cup size). Your actual volume of the rectangle has stayed the same it has just dispersed in a different direction.

If you view bra fitting as not just one size but a range then this allows you to get the better fit. Saying you are just are a D cup tells me nothing as you need the band size as well to relate to it.

A bra size needs will correspond to all the sizes next to it. so you can make decisions on fitting a bra.

Knowing that a 36B is a cup size bigger than a 34B yet both are a B cup. Looking at the table you can see that as well as a 36B being bigger than a 34B, a 36B is bigger than a 36A.

So, if you went and tried on a 34B and the band was fine but the cup too small you would choose a 34C

Cup volume

This is the letter in the bra and it is the volume in the cup that together with the band indicates the cup size.

Band size

This is the number in the bra and the measurement of the underband comes from measuring in a circumference around your rib cage.

With sister sizing you are adjusting the proportion of both the cup and the band to get the best fit.

If you imagine a bra as a rectangle and I needed to fit this rectangle bra and I needed to ensure that 10 squares of volume was covered. And I started with 34B to cover that 10 square volume, but it was too big around the back so I would then sister down to a 32C the volume of the bra is the same. And because I have done down to a 32 back I would need to go up in the front (as a 32B has a smaller cup than a 34B).

You haven’t altered the voulume of the cup.

A 32C is a narrower and deeper rectangle but has the same volume as a 34B

A 36A is a wider and shallower rectangle but has the same volume as a 34B

Note: If you go down on the cup you need to go up on the band

If you go down on the band you need to go up on the cup.

Those who do wear a bigger back than they are suppose to can find that they are wearing their breasts under their arm pits, and when they sister size, that breast tissue is pushed facing forward and you can seem like you have a smaller silhouette yet more boobs, however all you’ve done is alter the way where the breast tissue sat and is supported.