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Calculate your perfect bra size instantly with accurate measurements for band size, cup size, and sister sizes. Get international sizing support and expert fitting guidance.
Find your perfect bra size with accurate measurements and professional guidance
Measure directly under your bust, around the ribcage
Measure around the fullest part of your bust
Accurate measurements are the foundation of finding your perfect bra size. Follow these steps carefully for the best results.
Wrap a measuring tape snugly around your ribcage directly under your bust. Keep the tape parallel to the ground and breathe normally. Round to the nearest whole number.
Measure around the fullest part of your bust while wearing a non-padded bra. Keep the tape level and not too tight. Round to the nearest whole number.
Subtract band measurement from bust measurement. Each inch of difference equals one cup size: 1"=A, 2"=B, 3"=C, 4"=D, 5"=DD/E, etc.
If your band measurement is odd, add 1 inch. Try sister sizes if your exact size isn't available or doesn't fit perfectly.
Measure while wearing a non-padded, well-fitting bra or no bra at all for most accurate results.
A flexible fabric measuring tape gives more accurate results than a rigid ruler.
Maintain good posture and breathe normally while measuring for consistent results.
Having someone else measure you can provide more accurate and consistent measurements.
Avoid measuring during menstruation when breasts may be swollen or tender.
The band should sit parallel to the ground, not riding up your back. It provides 80% of support.
The center piece between cups should lie flat against your sternum without gaps.
No spillage at top, sides, or underarms. Breasts fill cups without gaping or wrinkling.
Straps don't dig in or slip off shoulders. You can fit two fingers under them comfortably.
Underwire sits in the crease under breasts, not on breast tissue, and follows natural curve.
No pinching, poking, or discomfort even after wearing for several hours.
If the band rides up your back, it's too loose. Try a smaller band size or tighten hooks.
Breasts spilling over means cups are too small. Gaping or wrinkling means cups are too large.
Digging straps mean band is too loose. Falling straps mean they need adjustment or band is too big.
If center piece floats away from chest, cups are too small or style doesn't suit your shape.
Underwire should never sit on breast tissue or poke into armpits. Try a different size or style.
Bulging around band indicates it's too tight. Size up in the band and adjust cup accordingly.
Smooth, seamless cups that don't show under clothing. Perfect for everyday wear and fitted tops.
Padded cups with angled padding to lift and enhance cleavage. Creates fuller appearance.
High support with compression or encapsulation design. Minimizes movement during exercise.
Horizontal cut with wide-set straps. Shows more décolletage while providing good support.
No straps, relies on band for support. Often has silicone grip to stay in place.
Soft, wireless, minimal support. Comfortable for lounging and light activities.
Easy-open clips for breastfeeding. Stretchy, comfortable fabric for changing breast size.
Very low center gore for deep V-necklines. Creates cleavage while staying hidden.
Covers entire breast with higher center gore. Maximum support and coverage.
To measure your bra size accurately: 1) Measure your band size by wrapping a measuring tape snugly around your ribcage directly under your bust, 2) Measure your bust size at the fullest part of your breasts while wearing a non-padded bra, 3) Calculate the difference between bust and band measurements to determine cup size. Each inch of difference equals one cup size (1"=A, 2"=B, 3"=C, etc.).
Sister sizes are alternative bra sizes that have the same cup volume but different band sizes. When you go up one band size, you go down one cup size, and vice versa. For example, if you wear 34C, your sister sizes are 32D (smaller band, larger cup) and 36B (larger band, smaller cup). Sister sizes are helpful when your exact size isn't available or you prefer a different fit.
Signs of a poorly fitting bra include: band riding up your back, straps digging into shoulders or falling down, cups gaping or overflowing, underwire poking or sitting on breast tissue, back bulges, breast spillage at sides, center gore not lying flat against sternum, and general discomfort.
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Medical Disclaimer:
This calculator provides general sizing guidance based on standard measurement methods. It is not a substitute for professional bra fitting services. If you experience persistent discomfort, pain, or have specific medical concerns related to breast health or support, please consult with a healthcare professional or certified bra fitting specialist.
About This Tool:
Our bra size calculator uses industry-standard measurement methods and sizing conventions. The calculations are based on established lingerie industry standards from organizations including ASTM International and the European Committee for Standardization (CEN). Individual results may vary based on body shape, breast shape, and brand-specific sizing variations.
Professional Fitting Recommended:
For the most accurate fit, we recommend getting professionally fitted at a lingerie boutique or department store with certified fitting specialists. Professional fitters can account for individual variations in breast shape, body proportions, and personal comfort preferences that automated calculators cannot assess.
Unlike other calculators, we provide complete sister size charts with detailed explanations of when and why to use them.
Accurate conversion between US, UK, EU, AU, and FR sizing systems - not just basic conversions.
Detailed visual guides showing signs of good and poor fit that competitors don't provide.
Guidance on different bra styles and when to wear them - information missing from most calculators.
Practical advice for women with different-sized breasts - a topic competitors often ignore.
Specific recommendations for pregnancy, nursing, sports, and different life stages.