Bra Sister Sizes: What to Do When Your Measured Size Doesn’t Fit

What Are Sister Sizes and Why Are They Important?

Sister sizes are your secret weapon when it comes to achieving the perfect bra fit. A sister size is an alternative combination of band and cup sizes that maintains the same cup volume but adjusts the band width. If you size the band up or down, you must adjust the cup size in the opposite direction to keep the fit proportional. 

Example: If your size is 34C but the band feels too loose, try a 32D the band is smaller, but the cup volume stays the same. If the band is too tight, try a 36B instead. 

How to Calculate Your Sister Sizes

From delicate lace to sheer mesh and intricate embroidery, the beauty of an Aubade bra truly comes to life with the right fit. To make the most of sister sizing, it's essential to know your actual bra size and how to interpret your bra’s fit. 

Measure Your Actual Bra Size 

Sister sizes only help if your original size is accurate. Breast size can change due to weight fluctuations, pregnancy, or hormonal shifts so it’s wise to measure regularly. Here’s how: 

• Band size: Measure tightly around your ribcage, directly under your bust, keeping the tape measure level. 
• Bust size: Measure loosely around the fullest part of your bust. 
• Cup size: Subtract your band size from your bust size. The difference determines your cup (A, B, C, D, etc.) using a size chart. 

Check Your Bra’s Fit

Ask yourself: 

• Does the band sit straight and snug without digging in? 
• Do the underwires lie flat against your chest? 
• Do the cups completely enclose your breast tissue? 
• Can you move comfortably without spillage? 

If your straps slip, wires dig in, or cups wrinkle, your bra size or a sister size might need adjustment. 

Choose the Right Sister Size

If your bra still doesn’t fit right despite matching your measurements, here’s how sister sizes can help: 

• Band feels too tight: Go up one band size and down one cup size → 36B instead of 34C 
• Band feels too loose: Go down one band size and up one cup size → 32D instead of 34C 

For cup fit: 

• Cups too small (spillage): Try one cup size up and one band size down → 32D instead of 34C 
• Cups too large (gaping): Try one cup size down and one band size up → 36B instead of 34C 

These adjustments keep the cup volume consistent while improving the overall fit. Sister size charts often available on brand websites make it easy to find your two alternative sizes based on your main size. 

Pro Tip: Try On Multiple Sizes & Check Brand Charts

Different lingerie brands and even different bra styles fit differently. A structured balconette bra may feel completely different from a stretchy bralette, even in the same size. That’s why it’s smart to: 

• Check the brand’s specific size guide 
• Try your measured size and both sister sizes 
• Consider fabric, stretch, and structure when choosing 

Conclusion: Say Goodbye to Ill-Fitting Bras with Sister Sizes

Sister sizes bring balance to your lingerie wardrobe and can solve the mystery when a measured bra size just doesn’t feel right. Whether you're wearing a balconette, push-up, or soft cup bra, knowing your correct size and your two sister sizes will help you find a bra that flatters your body, supports your bust, and feels amazing every single day.