Bra Size Calculator
Two tape measurements in inches. Out comes a US band size and cup letter.
How to Measure for Band and Cup
- Underbust: wrap the tape directly under your bust, level all the way around, snug but not digging in. Exhale normally, then read the number.
- Bust: measure around the fullest part, tape level and relaxed, without compressing.
Band size
The band is your underbust measurement rounded to the nearest even number, since US bands come in even sizes (30, 32, 34 and so on). This calculator uses the modern convention: no extra inches added to the underbust. Older charts add 2 to 4 inches, which tends to produce loose bands and undersized cups. If your number rounds down and the band feels tight, go up one band and down one cup.
Cup letter
The cup is the difference between bust and band, one letter per inch:
| Bust minus band | Cup |
|---|---|
| 0" or less | AA |
| 1" | A |
| 2" | B |
| 3" | C |
| 4" | D |
| 5" | DD |
| 6" | DDD (F) |
| 7" | G |
| 8" | H |
Worked example: underbust 31" rounds to a 32 band. A 36" bust is 4 inches over the band, which lands at D, so 32D.
Fit varies by brand
Treat the result as a starting point, not a verdict. Cut, style and country of origin all shift sizing, and past an H cup the lettering itself differs between labels, so the calculator points you to brand charts instead of inventing letters. More on how this site handles estimates is on the about page.