Bra size calculator: band, cup and sister sizes
Measure snugly around your ribcage just under your bust, then loosely around the fullest part of your bust. With the current method, the band is your underbust rounded to the nearest even number, and each inch of difference between bust and band is one cup size: 32 and 36 inches make a 32D.
Uses the current +0 method: band from your underbust rounded to the nearest even number, cup from the difference between bust and band in inches. Some brands still use the older +4 method, which adds 4 to 5 inches to the band and gives a smaller cup; if your usual size looks very different, that is usually why. Sizing is not standardized between brands, so try a sister size if the band or cup feels off.
How to measure
- Wear a non-padded bra, or none, and stand straight with your arms relaxed.
- Underbust: wrap the tape around your ribcage right under your bust. Keep it level and snug, and breathe out.
- Bust: wrap the tape around the fullest part of your bust, level all the way around, without squeezing.
Cup sizes, inch by inch
| Bust minus band | Cup |
|---|---|
| Less than 1 inch | AA |
| 1 inch | A |
| 2 inches | B |
| 3 inches | C |
| 4 inches | D |
| 5 inches | DD or E |
| 6 inches | DDD or F |
| 7 inches | DDDD or G |
Sister sizes
Cup volume is tied to the band. Going down one band size and up one cup keeps the same cup volume on a tighter band, and the reverse also works: 30DD, 32D and 34C hold the same cup volume. If the cups fit but the band rides up, try the sister size with a smaller band.
Why your size may not match your drawer
There is no binding standard between brands, and some still use the older +4 method, which adds 4 or 5 inches to the band and lands on a smaller cup letter. Letters above D also change from brand to brand. Treat the result as a starting point, and judge the fit by the band: it should sit level and snug on the loosest hook when new.