Bra Size Calculator
Calculate your bra size from your band and bust measurements. Convert between US, UK, and EU sizing. Get sister size recommendations.
Enter your measurements
How to Measure
Step 1: Measure your band (underbust)
Wrap a flexible measuring tape snugly around your ribcage, just below your breasts. Keep the tape level all the way around. The tape should be firm but not tight. Round to the nearest whole number.
Step 2: Measure your bust
Wrap the measuring tape around the fullest part of your bust. Do not pull the tape tight — it should rest gently against your body. Stand straight with your arms at your sides.
Tips for accurate measurement
- Wear an unpadded bra or no bra for the most accurate results
- Stand in front of a mirror to ensure the tape is level
- Breathe normally — do not hold your breath
- Measure twice to confirm your numbers
Size Chart Reference
| Difference (in) | US Cup | UK Cup | EU Cup |
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Frequently Asked Questions
How do I measure my bra size at home?▾
Measure your underbust (band) snugly around your ribcage just below your breasts, and your bust at the fullest point. Enter both measurements into the calculator to get your US, UK, and EU bra sizes instantly.
What are sister sizes in bras?▾
Sister sizes are bra sizes with the same cup volume but different band and cup combinations. For example, 34C has sister sizes 32D (band down, cup up) and 36B (band up, cup down). They can help you find a better fit.
How do US, UK, and EU bra sizes differ?▾
US, UK, and EU systems use the same band sizes but different cup labels after D. For example, US DD/E is UK DD and EU E. This calculator converts between all three systems automatically.
Is this bra size calculator accurate?▾
This calculator uses standard industry sizing formulas based on the difference between your bust and band measurements. For the best fit, we recommend trying on bras in your calculated size and sister sizes.
Is my measurement data stored or shared?▾
No. All calculations happen entirely in your browser. No data is ever sent to a server or stored anywhere.