Enter your bust measurement and band (frame) measurement to find your perfect bra size across US, UK, EU, France, and Australia/NZ sizing systems. Choose your preferred unit (inches or centimeters), input both measurements, and get your recommended bra size with cup and band details for every major region.
Your Bra Size (US/CA)
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UK Size
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EU Size
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FR / BE / ES Size
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Australia / NZ Size
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Band Size (inches)
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Cup Size
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Stand straight with your arms at your sides and wear a properly fitted bra. Measure loosely around the fullest part of your chest (usually across the nipples). Record the measurement to the nearest ¼ inch or ½ cm.
Measure firmly (but not tightly) directly underneath your breasts, where the bra band sits. Keep the tape parallel to the ground. This is sometimes called the 'frame size' or 'underbust measurement.'
Cup size is determined by the difference between your bust measurement and your band size. Each inch of difference corresponds to one cup size: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, and so on.
Different regions use different sizing conventions. The US and UK use the same cup letters but different band numbers; European (EU) sizes use centimeters for the band; French/Belgian/Spanish sizes add 15 to the EU band number; Australian sizes follow the UK cup system with different band numbers.
Studies and surveys suggest that anywhere from 70–85% of women wear incorrectly fitted bras. While exact figures vary by study, an ill-fitting bra can cause discomfort, poor support, and posture issues, making accurate measurement important.
US and UK bra sizes share the same cup letters (A, B, C, D, etc.) but the band sizes can differ by a few numbers. This calculator provides conversions for US/CA, UK, EU, FR/BE/ES, and Australia/NZ all at once.
If your measurements land between sizes, try both the smaller and larger size. Many women find they need to size up in the band if they're between sizes, or they can try a sister size (a different band/cup combination with equivalent volume).
Either works — this calculator accepts both. Inches are standard in the US and UK, while centimeters are commonly used for EU sizing. Just make sure both your bust and band measurements use the same unit.