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30B bra size — conversions, sister sizes & fit
A 30B fits an underbust of about 62.5–67.5 cm with a bust 11.25–13.75 cm larger than the band. Here is everything that label actually means — and how to check it really fits you.
Your bra size
30B US
Which measurements give 30B?
| cm | |
|---|---|
| Underbust (snug) | 62.5–67.5 |
| Bust (fullest point) | 73.75–81.25 |
| Difference (cup volume) | 11.25–13.75 |
Between two sizes? Measurements near the edges of these ranges can also fit the neighbouring size — check the sister sizes below and, in doubt, trust the fit checks from our measuring guide.
Sister sizes of 30B
28C and 32A hold a similar cup volume to 30B with a tighter or looser band. If the band of a 30B rides up, try 28C; if it digs in, try 32A.
Small bands with small cups are genuinely underserved on the high street: many mainstream brands start at a 65 or even 70 band, so a lot of what fits you sits in petite-focused or Asian-market lines. Avoid the classic trap of taking a bigger band to find a cup that exists — a loose band gives no support. Look for brands whose size range starts at your band, and use the sister size only as a fitting-room fallback.
30B in the Cherry Size catalogue In the Cherry Size catalogue, 261 of 617 brands have a recorded size range that includes 30B. That count uses each brand's band range and largest cup (the smallest cup is not recorded) and includes ranges not yet checked. Each of them cuts it differently: the app estimates the size to try at each brand, from your own measurements.In the app, your size is free, and so is your size at 3 brands you choose. Every brand, the fitting room, the wardrobe and the journal need a subscription, with a free trial for eligible new subscribers.
See 30B brand by brand30B in questions
What is 30B in European sizing?
A 30B corresponds to 65B in European sizing and 80B in French/Spanish sizing, by the usual correspondences. The conversion changes the band numbering, and from DD up the cup letter too (US DD = EU E); individual brands can differ.
Is 30B big or small?
It is one of the smaller sizes: a petite band with a shallow cup. Cup letters mean nothing alone: a cup only has a volume relative to its band, which is why 28C and 32A hold a similar volume to 30B.
My 30B doesn't fit — what should I try?
If the band rides up or feels loose, go to 28C. If the band digs in while the cup is fine, go to 32A. If the cup overflows, try one cup up in the same band; if it wrinkles empty, one cup down. Two minutes with the calculator gives you a fresh estimate.
Nearby sizes
Your size, everywhere you shop
Cherry Size keeps your measurements on your iPhone, translates them into 617 brands, tracks changes through pregnancy, nursing or weight shifts (with a subscription) — and never uploads a thing. In the app, your size is free, and so is your size at 3 brands you choose. Every brand, the fitting room, the wardrobe and the journal need a subscription, with a free trial for eligible new subscribers.
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