When it comes to finding a perfectly fitting bra, the struggle is real. Every brand fits a little differently, and even your go-to size might not feel right across different styles. That’s where bra sister sizes come in—a little-known secret that can help you finally get that just-right fit. Whether you’re in between sizes, feeling snug in your current band size, or shopping across different bra styles, understanding sister sizing can make finding your new bra a stress-free experience. Our bra experts dive into it:
What Is Sister Sizing?
Sister sizing refers to alternative sizes that share the same cup volume but differ in band size and cup letter. In other words, a sister size isn’t a completely different size—it’s a strategic swap that keeps the cup volume the same while shifting the band size up or down.
A Quick Example:
Let’s say you usually wear a 34C. If the band feels tight, you might try a 36B. If it feels too loose, you could size down to a 32D. These are your sister bra sizes. The volume in the cup remains about the same—only the band and letter shift to balance the fit.
Where Did Sister Sizing Come From?
Sister sizing evolved from the structure of bra sizes themselves. Because bras are measured using a combination of band size and cup size, adjusting one often requires adjusting the other to maintain balance. The system was created to provide women with more options, especially when they fall between bra sizes or when certain sizes are sold out.
The Importance of Sister Sizing
Knowing how bra sister sizes work is more than a helpful trick—it’s an essential part of finding a bra that actually fits your body.
The Benefits of Adjusting Band and Cup Sizes
If your current band size is too snug but the cups fit well, sister sizing lets you find a better-fitting band size without sacrificing cup volume. Similarly, if the cups feel a bit off but the band is perfect, a sister size can help you tweak just one element of the fit.
Overcoming Common Sizing Challenges
Ever found a bra you love, but your exact size is sold out? Knowing your sister bra sizes gives you more flexibility when shopping, especially online. It also helps you navigate inconsistencies between brands and styles. Felina designs bras to deliver comfort and support, but even our most loved pieces might fit slightly differently depending on the materials and construction.
How Can I Calculate My Sister Size?
Once you know your main size, finding your sister sizes is pretty simple. Use this simple guide below:
Step 1: Adjust the Band Size
Move up or down one band size. Going up in band size means you go down in cup letter, and going down in band size means you go up in cup letter.
For example:
- 34C → one band up, one cup down → 36B
- 34C → one band down, one cup up → 32D
Step 2: Understand Cup Volume
Cup size isn’t absolute—it changes with band size. A 32D has less volume than a 36D because the cup is designed to match the width of the band. That’s why a 34C and a 36B can hold the same cup volume.
Step 3: Use A Sister Sizing Chart
If this sounds confusing, don’t worry. There are plenty of bra sister size charts available, which can help you quickly spot your alternative sizes and shop with more confidence. You can also use our fit guide to find your perfect fit.
The Advantages of Sister Sizing
Felina’s goal is to help you find comfort that feels like a second skin with intimates that empower your everyday. Sister sizing supports that mission by providing:
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Enhanced comfort and support
Wearing an ill fitting bra can lead to digging straps, gaping cups, and band rides, equating to a bra you can’t wait to take off. Using your sister bra sizes can help you fine-tune your fit and prevent discomfort, especially during hormonal changes, weight fluctuations, or in styles with less stretch.
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Versatility in fit options
Sister sizing gives you more flexibility when exploring new styles. Want to try a wireless bra or something more structured like a balconette? Knowing your alternative sizes gives you more to work with—and increases the odds of a great fitting bra.
Sister Sizing Isn’t Just A Helpful Hack
Sister sizing is an empowering tool. With a little know-how, you can navigate the world of bra sizes with more ease, flexibility, and comfort. Whether you’re in between sizes or exploring new silhouettes, understanding your sister sizes brings you one step closer to your perfect fit.
Still not sure where to start? Our Fit Guide is a great place to begin. If you’re ready to find your new favorite bra, you can explore our newest bra arrivals here.