Bra Size Calculator
Calculate your perfect bra size with our free, easy-to-use calculator. Enter your measurements to get accurate sizing in US, UK, EU, and other international systems, plus sister sizes and expert fit recommendations.
📏Enter Your Measurements
Measure directly under your bust, where the band sits
Measure around the fullest part of your bust
Select your preferred bra sizing system
📋How to Measure Correctly
- Wear a non-padded bra or no bra for accurate measurements
- Use a soft measuring tape and keep it parallel to the ground
- Measure underbust snugly but not too tight, exhale naturally
- Measure bust loosely around the fullest part, standing straight
- Record measurements in either inches or centimeters consistently
No results to display. Please enter your measurements and click Calculate.
About Bra Size Calculator
What is a Bra Size Calculator?
A bra size calculator is an online tool designed to help women determine their correct bra size based on body measurements. By entering underbust and bust measurements, the calculator computes the appropriate band size and cup size according to various international sizing systems. Finding the right bra size is crucial for comfort, support, and confidence. Studies show that up to 80% of women wear the wrong bra size, leading to discomfort, poor posture, and inadequate support. A properly fitting bra can improve appearance, reduce back pain, and boost self-confidence.
Key Components of Bra Sizing
- Band Size: The number in your bra size (32, 34, 36, etc.) representing the measurement around your ribcage under the bust
- Cup Size: The letter in your bra size (A, B, C, D, etc.) indicating the difference between bust and underbust measurements
- Sister Sizes: Alternative sizes with the same cup volume but different band sizes, offering flexibility in fit
- International Conversions: Size equivalents across different countries' sizing systems (US, UK, EU, AU, etc.)
- Measurement Difference: The inches or centimeters between bust and underbust that determines cup size
- Sizing System: The regional standard used for bra sizing (varies by country and manufacturer)
Why Accurate Bra Sizing Matters
Wearing the correct bra size is essential for physical health, comfort, and appearance. A well-fitting bra provides proper support, preventing shoulder pain, back strain, and poor posture. It enhances natural shape, improves clothing fit, and boosts confidence. For women with larger busts, proper sizing is particularly important to distribute weight evenly and prevent tissue damage. During pregnancy, postpartum, weight changes, and aging, breast size fluctuates significantly, making regular measurements necessary. The right bra size can also improve athletic performance, reduce breast movement during exercise, and provide better long-term breast health outcomes.
How to Use This Bra Size Calculator
Our bra size calculator is designed for accuracy and ease of use, providing results in multiple international sizing systems. Follow these detailed steps for the most accurate results:
Step-by-Step Instructions
- Choose Your Measurement Unit: Select either inches or centimeters based on your measuring tape. Consistency is key - use the same unit for both measurements.
- Measure Your Underbust: Wrap the measuring tape directly under your bust, where the bra band sits. Pull snugly but don't compress. The tape should be parallel to the ground. Exhale naturally and record the measurement.
- Measure Your Bust: Wrap the tape around the fullest part of your bust, typically at nipple level. Keep the tape loose and parallel to the ground. Stand straight without arching your back. Record this measurement.
- Enter Your Measurements: Input both measurements into the calculator. Double-check for accuracy - even a half-inch difference can change your size.
- Select Your Sizing System: Choose your preferred sizing system (US, UK, EU, AU, FR, or JP). The calculator will show conversions for other systems as well.
- Calculate: Click the Calculate button to see your results, including your primary size, sister sizes, and international conversions.
- Review Sister Sizes: Check the sister sizes if you find your calculated size uncomfortable or unavailable. These offer the same cup volume with different band sizes.
- Save or Share: Export your results as CSV, share with shopping companions, or print for in-store reference.
International Bra Sizing Systems Explained
Bra sizing varies significantly across countries and regions. Understanding these differences is crucial when shopping internationally or buying from foreign brands. Our calculator supports all major sizing systems and provides accurate conversions.
US Sizing System
The United States uses inch-based measurements with band sizes in even numbers (30, 32, 34, etc.). Cup sizes progress as A, B, C, D, DD/E, DDD/F, G, H, etc. Band sizes are the underbust measurement rounded to the nearest even number.
- Band size 34 = approximately 34 inches underbust
- Cup progression: A (1 inch difference), B (2 inches), C (3 inches), D (4 inches)
- Common sizes: 34B, 36C, 32D, 38DD
UK Sizing System
The United Kingdom uses a similar system to the US but with slight differences in cup sizing, particularly for larger cups. Band sizes are also inch-based even numbers. UK sizing is often considered more consistent than US sizing.
- Band sizes identical to US (32, 34, 36, etc.)
- Cup progression: A, B, C, D, DD, E, F, FF, G, GG, H
- UK DD = US DD, but UK E = US DDD/F
European (EU) Sizing
European sizing uses centimeter-based measurements. Band sizes are typically underbust measurement in centimeters plus 10-15cm. Cup letters remain similar (A, B, C, D, etc.) but correspond to different measurements.
- Band size 70 ≈ US 32, 75 ≈ US 34, 80 ≈ US 36
- Calculated as: (underbust in cm) + 10-15cm
- Cup sizes follow similar letter progression but with metric differences
Australian (AU) Sizing
Australian sizing is based on the British system but with band sizes typically 4 numbers higher than US/UK sizes for the same underbust measurement. Cup sizing follows UK conventions.
- AU 12 ≈ US/UK 32, AU 14 ≈ US/UK 34
- Add 4 to US/UK band size to get AU size
- Cup letters identical to UK system
French (FR) Sizing
French sizing uses centimeter measurements similar to EU sizing but without the additional 10-15cm. The band size is approximately equal to the underbust measurement in centimeters.
- Band size 85 = approximately 85cm underbust
- FR 85 ≈ US 32, FR 90 ≈ US 34
- Cup sizing follows European conventions
Japanese (JP) Sizing
Japanese sizing combines elements of both Asian body types and Western sizing systems. Band sizes are underbust measurement plus 5, and cup sizing uses letters similar to Western systems but calibrated differently.
- Band sizes: 65, 70, 75, 80, 85, etc.
- JP 70 ≈ US 30, JP 75 ≈ US 32
- Cup sizes: A, B, C, D, E, F (progression similar but fits differ)
When to Use a Bra Size Calculator
Bra size calculators serve multiple purposes throughout a woman's life. Understanding when to remeasure ensures consistent comfort and proper support. Here are the most common scenarios where calculating your bra size is beneficial:
Life Changes & Body Fluctuations
Body changes throughout life significantly affect bra size. Regular recalculation ensures continued comfort and support during these transitions.
- Pregnancy & Breastfeeding: Breasts can increase 1-3 cup sizes during pregnancy and change further while nursing. Remeasure each trimester and after weaning.
- Weight Changes: Gain or loss of 10+ pounds often affects bra size. Measure after significant weight changes for optimal fit.
- Hormonal Changes: Menopause, hormone therapy, and birth control can alter breast size and shape. Annual measurements recommended.
- Post-Surgery: Breast reduction, augmentation, or reconstruction requires new sizing. Wait until healing is complete before final measurement.
- Age-Related Changes: Breast tissue changes with age. Remeasure every 2-3 years or when bras become uncomfortable.
Shopping Scenarios
Knowing your accurate size streamlines the shopping experience, whether in-store or online, and helps navigate size variations between brands.
- Online Shopping: Essential for buying bras online where you can't try before buying. Reduces returns and ensures better fit.
- International Purchases: Converting sizes when buying from foreign retailers or while traveling abroad. Prevents sizing confusion.
- First-Time Specialty Shopping: When upgrading from basic brands to specialty or luxury lingerie with more precise sizing.
- Sales & Bulk Buying: Confidence in your size allows taking advantage of sales without trying on. Stock up when you find styles that work.
- Gift Shopping: Helping partners or family members purchase the right size as a gift. Always measure recently for accuracy.
Comfort & Health Issues
Physical discomfort or health concerns often indicate incorrect bra size. Recalculating can resolve many common problems.
- Shoulder Pain: Straps digging in suggest too-small band or wrong size. Proper sizing distributes weight to the band, not straps.
- Back Pain: Improper support from wrong size contributes to back strain. Larger busts especially need correct sizing for spinal health.
- Breast Pain: Poorly fitting bras can cause breast pain, particularly during menstruation. Proper support reduces discomfort.
- Skin Irritation: Chafing, redness, or indentations indicate fit problems. Correct sizing prevents skin issues and improves comfort.
- Posture Problems: Wrong size affects posture. Proper support helps maintain healthy spinal alignment and reduces slouching.
Special Activity Needs
Different activities require specific support levels. Knowing your accurate size helps select appropriate bras for various purposes.
- Sports & Exercise: Sports bras require precise sizing for effective motion control. Too loose provides inadequate support; too tight restricts breathing.
- Professional Settings: Achieving a smooth, professional silhouette under work attire requires perfect bra fit and appropriate style selection.
- Special Occasions: Finding the right size ensures confidence in formal wear, backless dresses, and special event outfits.
- Maternity & Nursing: Specialized bras for pregnancy and breastfeeding demand accurate sizing as bodies change rapidly during this period.
- Medical Needs: Post-surgical bras, mastectomy bras, and compression bras all require precise sizing for therapeutic effectiveness.
Factors Affecting Bra Fit & Sizing
Perfect bra fit depends on more than just measurements. Understanding these factors helps achieve optimal comfort and support, even with the correct calculated size. Bra fit is both science and art - measurements provide the foundation, but personal comfort and brand differences require attention.
Brand & Style Variations
Different manufacturers have unique sizing standards, even within the same country. A 34C from one brand may fit differently than a 34C from another. Molded cups, balconette, full coverage, and push-up styles all fit differently despite the same nominal size. Always try new brands even if you know your size, and expect to adjust up or down a size with different styles. Luxury brands often size more precisely than mass-market brands.
Breast Shape & Density
Breast shape (round, teardrop, wide-set, close-set, etc.) affects how bras fit beyond simple measurements. Dense, firm tissue fits differently than soft tissue of the same volume. Some shapes need wider or narrower wires, deeper or shallower cups, or more center support. Asymmetry (different sizes on each side) is normal - fit the larger breast and pad the smaller if needed.
Bra Age & Wear
Bras stretch over time, especially the band. A properly fitting new bra should fasten on the loosest hook, allowing tightening as it stretches. Replace bras every 6-12 months with regular wear, or when bands no longer provide support on the tightest hook. Washing, heat, and body oils accelerate deterioration. Signs of worn bras: riding up back band, stretched-out straps, wire poking through fabric.
Time of Day & Monthly Cycle
Breast size fluctuates throughout the day and menstrual cycle. Many women are slightly larger in evenings due to fluid retention. Hormonal changes before menstruation can increase breast size by up to one cup. Consider measuring at a consistent time and accounting for cycle-related swelling. Some women keep both regular and premenstrual-sized bras for comfort.
Posture & Measurement Technique
Slouching or standing unnaturally affects measurements. Stand naturally straight without arching back or pulling shoulders back excessively. Keep arms relaxed at sides, not raised. Measure while breathing normally, not holding breath. The measuring tape should be parallel to ground and snug but not tight - you should be able to fit two fingers under easily. Having someone help ensures more accurate measurements than self-measuring.
Weight Distribution & Body Shape
Overall body shape affects how bra sizes translate to fit. Athletic builds, pear shapes, apple shapes, and hourglass figures all wear the same size differently. Rib cage shape (conical, barrel, narrow) influences band fit. Torso length affects where the band sits. These factors mean calculated size is a starting point - trying on remains essential.
Best Practices for Bra Sizing & Shopping
Following these proven strategies ensures you get the best fit, comfort, and value from your bra purchases. Expert fitters, lingerie specialists, and women's health professionals recommend these practices for optimal results:
Measure Regularly
Remeasure every 6 months or after any significant body change. Don't assume your size remains constant - bodies change with age, weight fluctuations, fitness levels, and life events. Keep a size history noting date, measurements, and brands that fit well. This helps identify patterns and makes shopping easier. Many specialty lingerie stores offer free fittings - take advantage of professional services annually.
Understand Sister Sizing
Sister sizes maintain the same cup volume but with different band-cup combinations. If 34C feels too tight in the band but cups fit, try 36B (larger band, smaller cup letter). If band is too loose but cups fit, try 32D (smaller band, larger cup). This flexibility helps when your exact size is unavailable or when fit isn't quite right. Sister sizing is particularly useful with style variations - some styles run tight or loose in the band.
Try Multiple Sizes
When shopping, grab your calculated size plus one band size up and down, and one cup size up and down. This gives six bras to try: your size, sister sizes, and near variations. Different styles and brands fit differently, so testing a range ensures finding the best fit. Don't be discouraged if your 'usual' size doesn't work in every brand - it's normal and expected due to manufacturing variations.
Check the Four Fit Points
For a properly fitting bra: 1) Band should be level all around, not riding up in back. Fasten on loosest hook when new. 2) Cups should encapsulate all breast tissue without spillage, gaping, or wrinkling. 3) Straps should stay in place without sliding but not dig into shoulders. Most support comes from band, not straps. 4) Center gore (between cups) should lay flat against chest. If it doesn't, cups are too small or wide-set.
Invest in Quality
Better-quality bras last longer and fit better. Invest in 3-5 high-quality bras rather than 10 cheap ones. Look for: sturdy fabric, reinforced seams, quality elastic, comfortable underwires (if applicable), and adjustable features. Hand wash or use lingerie bags in cold water to extend life. Air dry - heat destroys elastic. Rotate bras daily to let elastic recover between wears.
Know Your Breast Shape
Understanding your breast shape helps select styles that fit best. Are you full on top or bottom? Wide-set or close-set? Round or teardrop shaped? Different styles suit different shapes. For example, full-on-top breasts need more coverage; wide-set benefits from side support; close-set needs narrower center gores. Research bra styles recommended for your shape or consult professional fitters.
Don't Shop by Letter Alone
Cup size is relative to band size - a D cup on a 32 band is much smaller than a D cup on a 38 band. Focus on the full size (34DD) not just the letter. Avoid stigma about letters - they're just measurements. Many women are larger cup sizes than they realize because of the 80% wearing-wrong-size statistic. Embrace your actual size for better fit and comfort.
Document Your Perfect Fits
When you find a bra that fits perfectly, record the brand, style, size, and purchase date. Take photos of the tag and style details. Note how it fits at different points in your cycle. This information is invaluable for reordering or finding similar styles. Some brands discontinue styles, but if you know the fit characteristics you like, you can find comparable replacements.
Frequently Asked Questions About Bra Sizing
Q1:How accurate are online bra size calculators?
Online calculators provide a good starting point and are typically 80-90% accurate when measurements are taken correctly. However, they cannot account for breast shape, density, personal preference, or brand variations. Use calculated size as your baseline, then adjust based on fit. Professional in-person fittings may be more accurate but aren't always necessary unless you have unusual sizing needs or significant fit problems.
Q2:Should I measure with or without a bra?
For most accurate results, measure wearing a non-padded, well-fitting bra or no bra at all. Padded bras add volume that skews cup size calculations. Sports bras compress tissue and should be avoided. If you have larger breasts and need support while measuring, wear a thin, non-padded bra and note this when entering measurements, as it may slightly increase bust measurement.
Q3:Why do I have different sizes at different stores?
Bra sizing isn't standardized globally or even within countries. Different manufacturers have unique sizing standards, and various styles within the same brand may fit differently. Molded cups run differently than unlined; push-ups fit differently than full coverage. This is why trying on multiple sizes and styles is essential, even when you know your measurements. Always try before buying new brands or styles.
Q4:What if my measurements are between sizes?
When between sizes, round based on your needs. If between band sizes and prefer tighter support, round down; for more comfort, round up. Cup size between letters means trying both - one might fit better with certain styles. Sister sizing helps here too. If you're 33 underbust, try both 32 and 34 bands but adjust cup accordingly (34B and 32C are sister sizes with same cup volume).
Q5:How often should I replace my bras?
Replace bras every 6-12 months with regular wear (rotating 3-5 bras). Signs it's time: band rides up even on tightest hook, straps won't stay adjusted, wires poke through, cups wrinkle or gap, or it's simply uncomfortable. Bras worn more frequently wear out faster. Proper care extends life: hand wash or use lingerie bags, air dry, fasten hooks when storing, and rotate bras daily.
Q6:What are sister sizes and when should I use them?
Sister sizes are alternative sizes with the same cup volume but different band sizes. They work by going up a band size and down a cup, or vice versa. Example: 34C, 36B, and 32D are sisters. Use sister sizes when: your size is unavailable, the band feels slightly too tight or loose but cups fit, or when trying new brands that run differently. They provide flexibility without sacrificing cup fit.
Q7:Is it normal for breasts to be different sizes?
Absolutely - breast asymmetry is very common, affecting over 90% of women to some degree. Size differences of up to one cup size are normal. When fitting bras, always fit the larger breast and use removable pads or inserts in the smaller cup if needed. Some brands make bras specifically for asymmetry with different-sized cups, though these are specialty items.
Q8:Why does my bra band ride up in the back?
A rising band indicates the band is too large or worn out. The band provides 80% of support and should stay level. If a new bra rides up, try a smaller band size (and potentially larger cup to maintain cup volume through sister sizing). If it's an old bra, the elastic has stretched - time to replace it. The band should fit on the loosest hook when new.
Q9:Can I use this calculator if I'm pregnant or breastfeeding?
Yes, but expect frequent size changes during pregnancy and breastfeeding. Measure every trimester during pregnancy and every few weeks while nursing. Breasts can change dramatically during this time. Consider maternity and nursing bras designed for fluctuating sizes with more adjustability. Many women go up 1-3 cup sizes during pregnancy and change again after birth and weaning.
Q10:What's the difference between US and UK sizing?
US and UK sizing are very similar but diverge for larger cup sizes. Band sizes are identical (32, 34, 36, etc.). For cups A-D, sizing is the same. Differences start at DD and above: UK DD=US DD, but UK E=US DDD/F. UK continues: E, F, FF, G, GG, H, etc. US goes: DD, DDD/F, G, H, I. UK sizing is considered more consistent for larger cups. Always check which system a brand uses.