Question 1

Is bra band size based on underbust?

Accepted Answer

Yes, the band size starts with your underbust measurement in inches or centimeters, but different sizing systems round and label that measurement differently. US and UK systems add 4 or 5 inches to the underbust before rounding to the nearest even number, while EU sizing uses the underbust in centimeters directly. This means the same underbust can produce a different band number depending on which country's chart you are using, which is why a conversion tool like this is helpful for international shopping.

Question 2

Does this calculate cup size?

Accepted Answer

No, this converter focuses on band size only. Cup size requires both your underbust and bust measurements, plus the specific sizing system used by the brand. The cup letter is calculated from the difference between your bust and band measurements in inches, and that formula varies between US, UK, EU, and French sizing systems. For a full bra size conversion that includes both band and cup, use our separate Bra Size Converter tool instead.

Question 3

What if my underbust is between two bands?

Accepted Answer

If your underbust falls between two band sizes, try the smaller band if you prefer firm support and the larger band if you are sensitive to pressure or the bra fabric has less stretch. Many bras also have multiple hook-and-eye rows that allow minor size adjustments, and most people find they can wear two neighboring band sizes comfortably depending on the brand's construction and the fabric's elasticity.

Underbust	US/UK	EU	FR/ES	AU/NZ
26-27 in / 66-69 cm	30	65	80	8
28-29 in / 71-74 cm	32	70	85	10
30-31 in / 76-79 cm	34	75	90	12
32-33 in / 81-84 cm	36	80	95	14
34-35 in / 86-89 cm	38	85	100	16
36-37 in / 91-94 cm	40	90	105	18
38-39 in / 97-99 cm	42	95	110	20

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