Free Online Calculators
Underbust + bust → bra size EU and US with measuring guide
Tip: Measure snugly, horizontally, without a bra.
Getting the right bra size makes an enormous difference in comfort, posture, and confidence. Yet studies suggest that up to 80% of women are wearing the wrong bra size without even knowing it. Our free Bra Size Calculator takes the guesswork out of bra shopping by converting your underbust and bust measurements into both EU and US bra sizes instantly.
Accurate measurements are the foundation of a perfect fit. Before you use the calculator, grab a soft measuring tape and follow these steps carefully.
Wrap the measuring tape firmly around your torso, directly underneath your breasts. The tape should sit snug against your skin but not dig in. Keep it parallel to the floor all the way around. Breathe out normally and note the measurement in centimeters or inches.
Now wrap the measuring tape loosely around the fullest part of your chest, usually across the nipple line. Make sure the tape stays level across your back and does not pull or sag. Note this measurement as well.
Enter both figures into the Bra Size Calculator above, select your preferred unit (cm or inches), and hit Calculate. Your EU and US bra sizes will appear instantly.
Bra sizing systems vary across the world, which can make international shopping confusing. Here is a quick breakdown of the two most common systems.
In the United States, band sizes are expressed as even numbers (32, 34, 36, 38, and so on) and cup sizes run from AA through DDD and beyond. A US size 34B, for example, means a 34-inch band with a B cup.
European sizing uses centimeter-based band measurements (65, 70, 75, 80, and so on) paired with cup letters. The cup progression in the EU system is slightly different from US sizing, so a direct conversion is always helpful when buying from European brands.
Cup letters (A, B, C, D, etc.) generally correspond between systems, though extended cup sizes like DDD (US) are often labeled as E or F in European sizing.
The math behind bra sizing is straightforward once you know the formula.
For example, if your underbust is 76 cm and your bust is 89 cm, the difference is 13 cm (roughly 5 inches), which corresponds to a D cup on a 75 EU / 34 US band — giving you a final size of 75D (EU) or 34D (US).
Even with the right size on paper, fit can vary between brands and styles. Keep these practical tips in mind when trying on bras.
Your bra size is not fixed for life. It is worth recalculating whenever you experience significant body changes, including:
Experts recommend measuring yourself at least once a year and before any major bra shopping trip.
Sizing is not fully standardized across the industry. Different brands use slightly different grading systems, fabrics, and construction methods. Always try bras on when possible, or consult the brand-specific size chart and use our calculator result as a reliable starting point.
If your underbust measurement sits between two standard band sizes, try both and see which feels more comfortable. Many people also use sister sizing — for example, if a 34B feels tight in the band but the cup fits well, try a 32C, which has a smaller band but an equivalent cup volume.
Our Bra Size Calculator uses universally accepted measurement formulas and works for all body types. That said, body shape, breast position, and personal comfort preferences can influence the ideal style or cut of bra, even when the size calculation is correct.
Absolutely. The calculator supports both centimeters and inches. Simply select your preferred unit before entering your measurements and the tool will handle the conversion automatically.
Sister sizing refers to adjacent bra sizes that share the same cup volume but have different band sizes. For instance, 34B, 36A, and 32C are all sister sizes because the cup capacity is equivalent. Going up a band size means going down a cup letter, and vice versa. This is a useful trick when a perfect fit in one dimension leaves the other slightly off.