Bra Size
Calculator for Women
Find your accurate bra size using simple measurements. This free calculator provides US, UK, and EU sizes plus sister size options for the best fit.
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How This Bra Size Works
The calculator uses your underbust measurement to determine band size and the difference between bust and underbust to determine cup size. Each inch of difference corresponds to a cup size. Results include conversions for US, UK, and EU sizing systems plus sister sizes for alternative fits.
When Should You Use This Tool
Use this calculator before bra shopping, especially when buying online or trying a new brand. Remeasure every 6-12 months or after significant weight changes, pregnancy, or hormonal shifts. Wearing the correct size improves comfort and support.
Is This Tool Accurate and Safe
Bra sizing varies significantly between brands and styles. This calculator provides a starting point. The best fit often requires trying multiple sizes. Sister sizes (one band size down with larger cup or vice versa) often fit similarly. All measurements stay private in your browser.
Frequently Asked Questions
How do I measure my underbust correctly?
Wrap a measuring tape snugly around your ribcage directly under your breasts. The tape should be level all around and firm but not tight. Exhale normally and record the measurement.
How do I measure my bust correctly?
Wear an unpadded bra or no bra. Wrap the tape around the fullest part of your bust, keeping it level. Do not pull tight - the tape should just touch the skin all around.
What are sister sizes?
Sister sizes have the same cup volume but different band sizes. For example, 34C, 32D, and 36B are sister sizes. If your calculated size does not fit perfectly, try a sister size.
Why does my bra size vary between brands?
There is no universal bra sizing standard. Each brand creates their own patterns and sizing systems. A 34C in one brand may fit like a 32D or 36B in another. Always try before buying when possible.