B90 Bra Size, In Full
A Japanese B90 is a 90 cm band with a B cup: written cup-first, measured in 2.5 cm steps, and one letter ahead of the Western alphabet. In US terms this body wears a 40A.
B90 measurements
A Japanese B is not a Western B
Japanese cup labels start earlier and step in 2.5 cm increments, so each letter sits roughly one label ahead of its Western namesake: this B90 corresponds to a US 40A and EU 90A. Order your Japanese letter from a Western shop (or vice versa) and you’re a full cup off before the parcel ships. The converter translates in both directions.
Bands translate cleanly (same centimeters as EU labels); only the letters shift.
B90 sister sizes
Japanese sisters move in 5 cm band steps with one cup letter, same volume, different circumference. Useful when domestic stock stops one band short of yours.
What works at this size
At this volume nearly every style in Japanese ranges works, and Japanese ranges lean heavily on molded, lightly padded cups with soft wires. Choose by neckline; construction rarely limits you here.
B90: answered
What is Japanese B90 in US sizing?
US 40A (UK 40A). Japanese cup letters sit one label ahead of Western ones for the same body (a Japanese B corresponds to a Western A-tier cup) so carrying the letter across unconverted buys a cup too big.
What measurements is B90 for?
An underbust around 90 cm (roughly 87.5–92.5 cm) and a top bust near 102.5 cm: a difference of about 12.5 cm, which Japanese sizing labels B. Japan measures in 2.5 cm cup steps against Europe's 2 cm, so conversions are nearest-label, not exact.
Why is the cup letter written first in B90?
Japanese convention writes cup-then-band. C70, not 70C. Same information, reversed order; on tags in Japan you may also see the band alone (70) with the cup on a separate line.
HauteFlair labels cups in UK letters, so these links already convert your size by position (a US DDD lands on a UK E, a US G on a UK F). HauteFlair is owned by the same company as Brasize.ai; that relationship never changes the sizing math, charts, or fit advice on this page. How this site makes money.
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Two measurements, no inches added, sister sizes attached.
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