Calculate your bra size from band and bust measurements. Get UK, US, and EU sizing with sister size suggestions.
What Is Bra Size Calculator?
Bra sizing combines a band measurement (the number) with a cup measurement (the letter). The band size is the circumference around the ribcage just below the bust, and the cup size represents the difference between the bust measurement and the band measurement. However, sizing systems vary significantly between countries — a UK 34D is different from a US 34D and an EU 75D.
Poorly fitting bras are extremely common — surveys suggest that up to 80% of women wear the wrong size. This calculator uses your measurements to determine your size across different international systems and accounts for the differences between UK, US, EU and other sizing conventions.
Free results include UK, US and EU sizing. Premium adds your Australia/NZ size (identical to UK sizing), a sister-size list for when your exact size isn't in stock, and a fit-troubleshooting guide covering common signs of a poor fit (riding up, digging straps, gaping cups) and what each one usually means.
How to Use This Tool
Measure your underbust circumference (snugly around your ribcage, just below your bust).
Measure your bust circumference (at the fullest point, without compressing).
Enter both measurements in centimetres or inches.
View your recommended size in UK, US, EU and other sizing systems.
Check the sister sizes (adjacent sizes with equivalent cup volume) if your recommended size is not available.
Tips & Best Practices
The band should be snug on the loosest hook — it will stretch over time, and you can tighten it to the inner hooks.
Cup size is relative to band size — a 32D has a smaller cup volume than a 36D.
Sister sizes share the same cup volume: 34C, 32D and 36B all have the same cup volume.
Try on bras at the end of the day when your body is at its normal size for the most accurate fit.
Common Use Cases
Finding your correct bra size using body measurements.
Converting between UK, US and EU bra sizing systems for international shopping.
Understanding sister sizes when your exact size is not available.
Rechecking your size after weight changes, pregnancy or other body changes.
Frequently Asked Questions
How do I measure for my bra size?
Measure your ribcage snugly for the band, and around the fullest part of your bust. Enter both measurements to calculate your size.