B cup bra size
B stands for a 2 in difference between bust and band in US, UK, EU, FR/BE and AU/NZ; US also gives the equivalent as 5.1 cm.
In US sizing a B cup is a difference of 2 in (5.1 cm) between bust and band.
B at 2 in, system by system
A cup letter stands for a difference between bust and band. The same letter sits at a different difference in some systems.
| System | Difference (in) | Difference (cm) | Written as |
|---|---|---|---|
| US | 2 | 5.1 | B |
| UK | 2 | 5.1 | B |
| EU | 2 | 5.1 | B |
| FR/BE | 2 | 5.1 | B |
| AU/NZ | 2 | 5.1 | B |
| JP | Not used | Not used | Not used |
| EU method (cm) | Measured in cm | 14 to 16 cm | B |
Where sources disagree about B
The sources used here agree on this letter. They differ on other points, which the methodology page lists.
9 sizes carry a B cup
Every size page that has this cup.
B has a 2 in difference in US, UK, EU, FR/BE and AU/NZ, while the US chart gives its centimetre equivalent as 5.1 cm. The inch figure stays the same across those systems, whereas the EU method assigns B a separate centimetre interval. The Japanese chart has no letter B.
In the US, UK, EU, FR/BE and AU/NZ sequences, B sits between A and C. The Japanese chart omits B; its listed letters vary by brand and cover only part of the range.
For B, the EU method sets the bust minus band difference at 14 cm up to but not including 16 cm. This is the centimetre range associated with B in that method.
For cup B, band 32 pairs with a bust of 33.5 to 34.5 in (85.1 to 87.6 cm), and band 34 pairs with 35.5 to 36.5 in (90.2 to 92.7 cm). For cup B, band 36 pairs with a bust of 37.5 to 38.5 in (95.3 to 97.8 cm), and band 38 pairs with 39.5 to 40.5 in (100.3 to 102.9 cm). A comes before B and C follows it.
The published charts give the same inch difference for B and the same bust ranges on bands 32, 34, 36 and 38. The figures list no disagreement for B.
Questions
What does a B cup mean?
A B cup is a difference of 2 in (5.1 cm) between bust and band in US sizing. The letter names the size of that difference.
Which difference is a B cup in each system?
US 2 in, UK 2 in, EU 2 in, FR/BE 2 in, AU/NZ 2 in and JP does not use it.
Do all systems write a B cup the same way?
Not everywhere. In US sizing it is 2 in, and JP (not used) differ.