The Bra Size Calculator estimates bra size from bust and band (underbust) measurements and shows equivalent sizes in US, UK, EU, French and Australian systems.
Your bra size: 34D (US)
| US/CA | 34D |
| UK | 34D |
| EU | 85D |
| FR/BE/ES | 100D |
| Australia/New Zealand | 12D |
| Band | 34 in |
| Cup difference | 4 in |
Band: measure snugly around the ribcage just under the bust, keeping the tape level. Bust: measure loosely around the fullest part of the bust while wearing a non-padded bra. Breathe normally and use a soft tape measure.
The band size is the underbust measurement rounded to the nearest even number. The cup letter comes from the difference between bust and band: 1 inch = A, 2 = B, 3 = C, 4 = D, 5 = DD, and so on.
Worked example (defaults): band 34 in and bust 38 in give a 4-inch difference, so the size is 34D in the US.
UK sizes use the same band numbers but different cup letters above D (DD, E, F, FF…). EU bands are in centimetres in steps of 5. French and Spanish sizes add 15 to the EU band. Australian sizes subtract 22 from the inch band. Brands vary, so always try on.
The band rides up the back (too loose), straps dig in (band too loose or straps too tight), cups gape (too big) or spill (too small), or the centre gore does not lie flat.
What are sister sizes? Going down a band and up a cup keeps the same cup volume (34D ≈ 32DD ≈ 36C).
How often should I re-measure? Every 6–12 months or after weight change or pregnancy.
Some methods add 4 inches to the band; which is right? Modern fitters usually do not add inches.