Bra Size Calculator

Find your bra size from band and bust measurements using UK, US, EU, and AU sizing charts.

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Enter your measurements Provide your band and bust measurements to estimate your bra size.

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Fashion & Sizing

How bra sizing works across UK, US, EU, and AU standards

A bra size calculator converts band and bust measurements into a bra size for multiple international sizing systems. Understanding how sizing differs across regions helps you shop online with confidence and avoid costly returns.

How bra size is determined

Bra sizing uses two measurements: the band (underbust circumference) and the bust (fullest part of the chest). The band measurement determines the band size, while the difference between bust and band determines the cup size. Each inch or centimetre of difference maps to a cup letter, though the exact mapping varies by country.

UK and US systems use inches and share band numbers, but cup letter progressions diverge after D. The EU system uses centimetres and rounds to the nearest five for the band. AU sizing closely follows UK conventions but can vary by brand.

Sister sizes and fit adjustments

Sister sizes have the same cup volume but a different band length. For example, a 34C has the same cup volume as a 32D or a 36B. If a bra fits in the cup but the band is too loose or tight, trying a sister size can solve the problem without changing the cup volume.

Fit also depends on bra style, fabric stretch, and brand-specific sizing. Measurements provide a starting point, but trying on multiple sizes is normal and expected.

Frequently asked questions

How often should I remeasure my bra size?

Body shape changes with weight fluctuations, hormonal cycles, pregnancy, and ageing. Remeasuring every six to twelve months, or whenever a bra starts feeling uncomfortable, is a practical guideline.

 Why do different brands fit differently in the same size?

There is no universal standard enforced across manufacturers. Cup depth, wire width, gore height, and fabric stretch all vary by brand and style, so a 34D from one maker may fit differently from another.

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