👙 Bra Size Calculator
Enter your underbust and bust measurements to estimate your band size and cup size using the standard bra-sizing method.
How bra sizing works
A bra size has two parts: the band size, based on your ribcage measurement just under the bust, and the cup size, based on how much larger your bust measurement is than your band measurement.
How this calculator works
Band size is found by rounding your underbust measurement to the nearest whole inch, then adding 4 if that number is even or 5 if it’s odd, which brings it to the nearest standard even band size. Cup size is found from the difference between your bust and underbust measurements: each full inch of difference steps up one cup letter (0″ = AA, 1″ = A, 2″ = B, 3″ = C, 4″ = D, and so on).
For best accuracy, measure both circumferences with a soft tape measure while wearing a well-fitting, non-padded bra, keeping the tape level and snug but not tight.
Sizing can vary meaningfully between brands and styles, so treat this as a helpful starting point rather than an exact fit — trying on is still the most reliable method.