Most bra discomfort has nothing to do with your body and everything to do with sizing. Studies on fitting-room data consistently find that the majority of women are wearing a band that runs too large and a cup that runs too small — a mismatch that shows up as strap-digging, underwire poking, and cups that never quite sit right. This guide is where that gets fixed. Below you’ll find our core fitting resources, in the order we recommend working through them if you’re starting from scratch.
In This Guide
| Guide | What It Covers | Status |
|---|---|---|
| How to Measure Your Size | Band and bust measurement at home, no fitter required | Available |
| Size Conversion Charts | Converting between US, UK, EU, and international sizing | Available |
| Sister Sizing Explained | Why the same cup can fit differently across bands | Available |
| Fit Troubleshooting | Diagnosing and fixing gapping, spillage, and riding up | Available |
Why Fit Comes Before Style
A bra that’s the wrong size will look and feel wrong regardless of how well-made or expensive it is. Two numbers drive everything: the band measurement, taken snug around your ribcage directly under the bust, and the bust measurement, taken across the fullest part of your chest. The difference between the two determines your cup size — and that difference changes as your band size changes, which is the entire premise behind sister sizing.
Getting this right isn’t a one-time event, either. Body composition shifts with weight changes, hormonal cycles, pregnancy, and simply the natural wear of elastic over time. A band that fit perfectly a year ago may have stretched out enough to sit differently today. We recommend re-measuring roughly every six months, or any time a bra that used to fit starts riding up in the back.
Signs You’re Wearing the Wrong Size
- Band rides up in the back. The band should sit level, parallel to the floor. If it climbs upward, the band is too large.
- Underwire sits on breast tissue instead of around it. The wire should lie flat against your ribcage at the center and sides — if it’s resting on tissue anywhere, the cup is too small.
- Straps dig in or constantly slip. Digging usually means the band is doing too little work and the straps are compensating; slipping often points to a strap or shoulder-shape mismatch rather than the band itself.
- Center gore doesn’t lie flat against your sternum. If it’s floating above your skin, the cup size is too small for your shape.
- Cup gapping or spillage. Gapping at the top means the cup is too big; spillage at the top or sides means it’s too small.
How We Approach Fit Advice
Every guide in this section is written to be usable without a professional fitting appointment — just a soft measuring tape and about five minutes. We update sizing charts and brand-specific notes as manufacturers revise their size ranges, and we flag when a brand’s fit runs notably small, large, or narrow compared to standard sizing.
Frequently Asked Questions
How often should I get remeasured?
About every six months, or after any significant weight change, pregnancy, or if a well-fitting bra suddenly feels different.
Can I measure myself accurately, or do I need a professional fitting?
Self-measurement at home is accurate for most people when done correctly — our measuring guide walks through the exact method. A professional fitting is most useful if you’ve tried multiple sizes and still can’t find a comfortable fit.
Why do I wear different sizes in different brands?
Sizing isn’t standardized across manufacturers the way shoe or clothing sizing loosely is. Cup shape, band stretch, and wire shape all vary by brand, which is why we include brand-specific fit notes wherever possible.
What is sister sizing and when should I use it?
Sister sizing lets you move to a different band size while keeping the same cup volume (for example, sizing down in the band while sizing up in the cup). It’s useful when a size is out of stock or when a brand’s specific fit runs differently than your usual size.