Enter your bust size and band size (frame size) to find your correct bra size. Choose your preferred unit (inches or centimeters) and region — US/CA, UK, EU, FR/BE/ES, or Australia/NZ — to get a size recommendation that matches your local sizing system. Measure your bust loosely around the fullest part of your chest, and your band snugly just beneath your breasts for the most accurate result.
Your Bra Size
--
Band Size
--
Cup Size
--
Bust–Band Difference
--
Stand straight with your arms at your sides, wearing a properly fitted bra. Wrap a soft measuring tape loosely around the fullest part of your chest (over the nipple line). The tape should be level all the way around and snug but not tight. Record to the nearest ¼ inch or ½ cm for best accuracy.
Measure firmly — not tightly — directly underneath your breasts, keeping the tape parallel to the ground. This is your underbust measurement. Round to the nearest ¼ inch or ½ cm. In many sizing systems, the band size is this measurement rounded up to the next even number.
The bust size is the circumference around the fullest part of your chest, while the band size is the circumference just beneath the breasts. The difference between these two measurements determines your cup size — each inch of difference typically corresponds to one cup size (A, B, C, D, etc.).
Different countries use different sizing standards. US/CA sizes use a lettered cup with an even band number (e.g. 34B). UK sizing is similar but cup progressions differ at larger sizes. EU sizing uses centimeters for the band. French/Spanish/Belgian and Australian systems each have their own numerical conventions, which is why converting between regions is important when shopping internationally.
Studies and surveys suggest that between 70–85% of women wear incorrectly fitted bras, though the exact figure varies by study and methodology. Common issues include bands that are too loose, cups that are too small, and straps adjusted to compensate for a poor fit. Getting professionally measured or using a calculator with accurate measurements can help.
It is a good idea to remeasure every 6–12 months, or whenever your body changes — after weight gain or loss, pregnancy, breastfeeding, or hormonal changes. Bra elasticity also changes over time, so a size that fit well a year ago may no longer be the best fit.
Yes. The band size conversion between US and UK is generally the same number, but cup sizes diverge at D and above (e.g. US DD = UK E). EU sizing uses the underbust measurement in centimeters, so a US 34B is roughly an EU 75B. This calculator shows your size in your chosen regional format based on your measurements.
The cup size letter represents the difference between your bust measurement and your band size. A difference of about 1 inch equals an A cup, 2 inches a B cup, 3 inches a C cup, 4 inches a D cup, and so on. Larger differences correspond to larger cup letters, though labeling varies slightly by region and brand.