Bra Sister Sizing

What is a sister size?

All expert bra fitters will tell you, you don't just have ONE size, you have up to THREE options when finding your fit. You may have noticed at the end of the Online Fitting Room or The Fit Finder Quiz you are given two sizes, one is your True Size and the other is your Sister Size.

How do you calculate a sister size?

“Sister Sizing” is all about the volume. If you’re happy you’ve got your cup size perfected, but something’s just not feeling right with the fit, this will sort you out. If you like to wear your band a little snug, you can go down a band size and up a cup size OR if you prefer things loose and free go up a band size and down a cup size. For example if you are a 34D, your sister sizes would be 32E and 36C. Making sense? No matter the band size or the cup letter swaps, the volume does not change.
If this is a little bit too much maths than you bargained for when bra shopping, use our sister size chart below. Start with your current size: If your band is the fit issue here, go across the chart and if your cups don’t fit, move up or down.
With Free UK Returns, we recommend buying both your true size and you sister size, keeping the one that fits you best and returning the other, free of charge.

Bra Sister Size Chart