What are the sister sizes of 40A?

38B — same cup volume, different band.

Is 40A the same in every brand?

No. A 40A 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.

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

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

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

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 40A

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

38B

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

Check my size →

Brands that make A-cup bras

40A FAQ

What is 40A in EU sizing?: 40A (US) is EU 90A. In UK sizing it is 40A. 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 40A?: 38B — same cup volume, different band.
Is 40A the same in every brand?: No. A 40A 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.