Calculate your bra size from two simple measurements: your bust circumference (at the fullest point) and the circumference right under the bust (underbust), both in centimeters.
How to measure
Bust: wrap the tape around the fullest part of your bust, without squeezing, wearing a bra you already use. Underbust: wrap the tape right below the bust, keeping it level and snug.
How the calculation works
The band (BR/EU numbering) is calculated by rounding the underbust measurement to the nearest multiple of 5 (for example, 78cm becomes band 80). The cup is set by the difference between bust and underbust: each 2cm of difference corresponds to one cup letter, starting at AA.
Bust-underbust difference → cup table
| Difference (cm) | Cup |
|---|---|
| 10-11 | AA |
| 12-13 | A |
| 14-15 | B |
| 16-17 | C |
| 18-19 | D |
| 20-21 | DD/E |
| 22-23 | F |
| 24-25 | G |
| 26-27 | H |
BR/EU vs. US/UK numbering
Brazilian and European sizing uses the rounded underbust in centimeters (e.g. band 80, 85, 90). American and British sizing instead uses inches with a traditional add-on (adding 4 or 5 to the underbust in inches, depending on whether it is even or odd), resulting in numbers like 34, 36, 38.
Frequently asked questions
Why does the result show two different numbering systems?
Because each region uses a different convention for the band: BR/EU uses rounded centimeters, while US/UK uses inches with the traditional add-4/add-5 method.
Is the cup letter the same in every country?
Generally yes for the first letters (A, B, C, D), but from DD/E onward some European brands use different letters (E, F, FF, G...) — check the specific brand's chart.
Is this result 100% accurate?
It is a solid starting estimate based on a widely used traditional method, but fit varies by brand and style — always confirm by trying the bra on.