What are the sister sizes of 40B?

38C and 42A — same cup volume, different band.

Is 40B the same in every brand?

No. A 40B can fit differently between brands because of pattern, fabric and cup shape. Use it as a starting point and try a sister size when switching brands.

40B bra size — conversion chart, sister sizes & brands

A 40B bra (US notation) in every regional standard. The same band-and-cup, labelled eight different ways.

US	UK	EU	FR	IT	AU	JP	IN
40B	40B	90B	105B	90B	18B	90B	40B

Band conversions are exact; cup fit still varies by brand, style, and body — a conversion is a starting point, not a guarantee.

Sister sizes of 40B

Sister sizes hold the same cup volume with a different band — the quickest fix when a band feels too tight or too loose.

38C 42A

Not sure you're a 40B? Two measurements, two minutes — free, nothing stored.

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Brands that make B-cup bras

40B FAQ

What is 40B in EU sizing?: 40B (US) is EU 90B. In UK sizing it is 40B. Band conversions are exact; cup fit still varies by brand, style, and body — a conversion is a starting point, not a guarantee.
What are the sister sizes of 40B?: 38C and 42A — same cup volume, different band.
Is 40B the same in every brand?: No. A 40B can fit differently between brands because of pattern, fabric and cup shape. Use it as a starting point and try a sister size when switching brands.