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40DD bra size — conversions, sister sizes & fit
A 40DD fits an underbust of about 87.5–92.5 cm with a bust 18.75–21.25 cm larger than the band. Here is everything that label actually means — and how to check it really fits you.
Your bra size
40DD US
Which measurements give 40DD?
| cm | |
|---|---|
| Underbust (snug) | 87.5–92.5 |
| Bust (fullest point) | 106.25–113.75 |
| Difference (cup volume) | 18.75–21.25 |
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 40DD
38DDD and 42D hold a similar cup volume to 40DD with a tighter or looser band. If the band of a 40DD rides up, try 38DDD; if it digs in, try 42D.
Deep cups on standard bands are well covered by full-bust specialists and increasingly by mainstream brands' extended ranges — but cut quality varies enormously. Prioritise firm bands (the band does most of the work, and that matters more with more weight to support), side support panels that keep tissue forward, and top edges that don't cut in. If straps dig, the band is almost always the real culprit.
40DD in the Cherry Size catalogue In the Cherry Size catalogue, 325 of 617 brands have a recorded size range that includes 40DD. 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 40DD brand by brand40DD in questions
What is 40DD in European sizing?
A 40DD corresponds to 90E in European sizing and 105E 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 40DD big or small?
It is a full-bust size: a deep cup on a standard band, well served by specialist lines. Cup letters mean nothing alone: a cup only has a volume relative to its band, which is why 38DDD and 42D hold a similar volume to 40DD.
My 40DD doesn't fit — what should I try?
If the band rides up or feels loose, go to 38DDD. If the band digs in while the cup is fine, go to 42D. 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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