Bra Size Calculator
Estimate your bra size from your underbust (band) and bust measurements. The band comes from your underbust rounded to the nearest even inch, and the cup from the difference between bust and underbust — about one cup size per inch.
Formula
Band = underbust rounded to the nearest even inch; Cup = (bust − underbust) in inches, where each inch ≈ one cup size
- Your band size is the underbust measurement converted to inches and rounded to the nearest even number.
- Your cup size comes from the difference between your bust and underbust: roughly one cup letter per inch of difference.
- Measure the underbust snugly just beneath the bust, and the bust loosely across the fullest part, both level to the floor.
- Cup-letter conventions vary between UK, US, and EU brands, so use the result as a starting point and try sister sizes for fit.
- This is an estimate for shopping convenience — a professional fitting gives the most reliable result.
75 cm underbust, 90 cm bust
Inputs
- Underbust (band) measurement: 75 cm
- Bust (fullest part) measurement: 90 cm
75 cm ≈ 29.5 in rounds to a 30 band, and a 15 cm (≈ 6 in) difference gives about a DD/E cup — roughly a 30E.
Frequently asked questions
How is my band size determined?
Your underbust measurement is converted to inches and rounded to the nearest even number, which becomes your band size.
How is cup size calculated?
Subtract your underbust from your bust measurement. Each inch of difference corresponds to roughly one cup size up from AA.
Why do different brands fit differently?
Cup-letter systems and grading differ between UK, US, and EU labels, so the same letter can fit differently. Try sister sizes if the fit is off.
How should I measure accurately?
Measure the underbust firmly just below the bust and the bust loosely at its fullest point, keeping the tape level all the way around.
Is this a substitute for a fitting?
No. It's a quick estimate. For the best fit, especially for sizing problems, a professional bra fitting is recommended.