Bra Size Calculator | Band, Cup and Region Conversion
Calculate an estimated bra size from underbust and bust measurements, with US, UK, EU, and AU/NZ size references.
Estimated Bra Size
Calculate Bra Size from Bust Measurements
Enter underbust and bust measurements to estimate band size, cup size, and regional sizing references for US, UK, EU, and AU/NZ systems.
Fit Depends on More Than Numbers
Shape, brand, fabric, style, strap position, and personal comfort can change the best size. Use the result as a fitting starting point.
When Bra Size Estimates Help
Use it before online shopping, comparing regional size charts, checking measurement changes, or preparing a first fitting size to try.
About This Tool
Bra Size Calculator determines your bra size from band and bust measurements in centimetres or inches and converts between UK, US, EU, and international sizing systems.
When to Use It
Use this when buying a bra online and you are unsure of your size, when converting between sizing systems across different brands, or after a significant change in body shape.
How to Use
- Measure your band snugly under your bust.
- Measure your bust at the fullest point.
- Enter both measurements and select your unit.
- Click Calculate to see your size across different sizing systems.
Frequently Asked Questions
Why do bra sizes vary between brands?
Brands manufacture to their own templates. A 34B in one brand may fit differently than a 34B in another. Use measurements as a starting point and check fit in person.
What is sister sizing?
Sister sizes are adjacent sizes with the same cup volume but different band widths. Going up one band and down one cup gives an equivalent fit.
How often should I remeasure?
Remeasure whenever weight changes significantly, after pregnancy, or if current bras feel uncomfortable.