Cherry SizeCalculator › All bra sizes, size by size › 40B
40B bra size — conversions, sister sizes & fit
A 40B fits an underbust of about 88–92 cm with a bust 11–14 cm larger than the band. Here is everything that label actually means — and how to check it really fits you.
Your bra size
40B US
Which measurements give 40B?
| cm | |
|---|---|
| Underbust (snug) | 88–92 |
| Bust (fullest point) | 99–106 |
| Difference (cup volume) | 11–14 |
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 40B
38C and 42A hold the same cup volume as 40B with a tighter or looser band. If the band of a 40B rides up, try 38C; if it digs in, try 42A.
This is one of the easiest profiles to shop: nearly every brand carries it. Your bigger risk is fit quality rather than availability — small cups on standard bands are often cut for a rounder shape than many bodies have, so gaping at the top edge is common. Balconette and demi cuts tend to follow a shallower curve better than full-coverage styles, and a band that stays put matters more than the cup label.
Who makes 40B? 316 of the 632 brands in the Cherry Size catalogue are confirmed to carry 40B in their standard range. But each of them cuts it differently — the app tells you the exact size to try at every one of them, from your own measurements.
See 40B brand by brand40B in questions
What is 40B in European sizing?
A 40B corresponds to 90B in European sizing and 105B in French/Spanish sizing. The cup volume is identical — only the band numbering changes between systems.
Is 40B big or small?
It is a common band with a shallower cup — widely stocked and easy to find. Cup letters mean nothing alone: a cup only has a volume relative to its band, which is why 38C and 42A hold exactly the same volume as 40B.
My 40B doesn't fit — what should I try?
If the band rides up or feels loose, go to 38C. If the band digs in while the cup is fine, go to 42A. If the cup overflows, try one cup up in the same band; if it wrinkles empty, one cup down. Two minutes with the calculator confirms it.
Nearby sizes
Your size, everywhere you shop
Cherry Size keeps your measurements on your iPhone, translates them into 632 brands, tracks changes through pregnancy, nursing or weight shifts — and never uploads a thing.
Download on the App Store