Bra Size Calculator

Bra Size Calculator — How to Measure & Convert

Finding the right bra size requires two measurements: your underbust (band size) and your bust (cup size). This calculator converts your centimetre measurements into US, UK, EU, and FR/BE bra sizes.

How to measure

Underbust (band): Wrap a tape measure around your ribcage directly under your breasts. Breathe normally. The tape should be snug but not tight.
Bust: Measure around the fullest part of your bust, keeping the tape parallel to the ground.

Band size calculation

Convert underbust cm to inches: cm ÷ 2.54
Round up to the nearest even number in inches — this is your US/UK band size
EU band = underbust cm + 15 (rounded to nearest 5)
FR/BE band = EU band + 15

Cup size from bust–band difference (US/UK)

Difference (inches)	US Cup	EU Cup
≤0	AA	AA
½	A	A
1½	B	B
2½	C	C
3½	D	D
4½	DD	E
5½	DDD/E	F
6½	F/G	G

Sister sizes

Sister sizes have the same cup volume but different band sizes. For example, 34C = 36B = 32D. If your band size doesn't feel right, try a sister size.

References

Greenbaum AR et al. (2003). "Breast measurement and sizing: a systematic review." Aesthetic Plast Surg 27:403–408.
Mason BR, Page KA, Fallon K (1999). "An analysis of movement and discomfort of the female breast during exercise." J Sci Med Sport 2(2):134–144.