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Bra Size Calculator

Measure snugly under the bust and around the fullest part of the bust, in centimetres.

cm

Wear an unpadded bra and keep the tape level. Measure snugly but comfortably.

cm

This result is an estimate only. Double-check important figures before relying on them.

How it is calculated

  • Band = underbust in inches, rounded to the nearest even number
  • Difference = bust − underbust in inches
  • Cup letter from the difference: 1 A, 2 B, 3 C, 4 D, 5 DD, 6 DDD (US) or E (UK) and so on

For other sizes, see the shoe size converter.

Worked example

Underbust 72 cm (28.3 in), bust 80 cm (31.5 in):

  • Difference about 3.1 inches, so a C cup
  • 28C in US and UK

Why your number may differ

A professional fitting is the most reliable. Pregnancy, weight changes and different brands change the best size.

Frequently asked questions

How is bra size calculated?

The band is your underbust in inches rounded to an even number. The cup comes from the difference between bust and underbust: 1 inch is A, 2 is B, 3 is C and so on.

Why does my size differ between brands?

Brands cut and size differently, and sister sizes exist, such as 34B and 36A, which fit similar cups. Try a few sizes.

Should I add inches to the band?

Older methods added 4 inches. Modern fitters use the underbust directly, which this calculator does.

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