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The Bra Bible Sizes · Styles · Fit Find your size
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Fit & Sizing

Bra Size Calculator

Enter two measurements and get your size instantly — US, UK, EU and AUS conversions, sister sizes included. No sign-up, nothing stored.

Bra Size Calculator

Enter two measurements and get your size instantly.

How the calculator works

Measure your underbust snugly in inches for the band, then measure around the fullest part of your bust. The difference between the two numbers is your cup: 1 inch is an A, 2 inches a B, 3 inches a C, 4 inches a D, 5 inches a DD, and up from there. The calculator rounds your band to the nearest even number, the way most fitters do, and shows the sister sizes that hold the same cup volume.

Nothing you type is sent anywhere — the maths runs in your browser and no data is stored.

Measure properly in three steps

  1. Wear an unpadded bra, or none at all, and stand in front of a mirror.
  2. Keep the tape snug and level — firm enough to stay put, not tight enough to bite.
  3. Breathe out before you read the number, and re-measure twice if the two readings disagree.

Then read the full bra fitting and sizing guide for conversions and the signs your size has changed.