Bra Size Calculator

Find your size in US, UK, EU, FR/ES, and AU/NZ systems · Updated March 2026

Bra Size Calculator

Enter your underbust (band) measurement and bust measurement below to calculate your bra size across five international sizing systems.

Your Results

Enter your measurements above and click "Calculate My Size" to see results here.

How to Measure

Accurate measurements are the foundation of a good fit. You will need a soft, flexible measuring tape. If you do not have one, use a piece of string and then measure the string against a ruler.

Sister Sizes Chart

Sister sizes share the same cup volume with different band sizes. When you move down one band size, the cup letter goes up one letter to maintain the same volume. This chart shows common sister size groupings across the standard range.

International Size Conversion

Bra sizing systems differ between countries. This table shows equivalent sizes across the five most common systems. Band numbers and cup letters do not translate one-to-one, so use this chart when ordering from international brands.

Common Fit Issues

Even with the correct calculated size, fit can vary between brands and styles. Here are the most common bra fit problems and how to solve them.

How Bra Sizing Works

Bra sizing combines two measurements into a single size code. Understanding the system helps you troubleshoot fit issues and navigate different brands.

Band Size

The band size is a number that corresponds to your underbust measurement. In US and UK sizing, the band number is your underbust measurement rounded to the nearest even number. Some older methods added 4 inches to the underbust measurement, but modern bra sizing no longer uses this approach. European band sizes use a different numbering system: a US/UK 32 is an EU 70, a 34 is an EU 75, and so on, incrementing by 5 for each band size increase.

Cup Size

The cup size is determined by the difference between your bust measurement and your band size. Each inch of difference roughly corresponds to one cup size. A 1-inch difference is an A cup, 2 inches is a B cup, 3 inches is C, 4 inches is D, 5 inches is DD (or E in UK sizing), and the letters continue from there. US and UK sizing diverge after US uses DDD then goes to G, while UK uses E, F, FF, G, GG, and so on. EU sizing uses sequential letters but skips some.

Cup Volume Is Relative

A critical concept in bra fitting is that cup volume is relative to band size. A D cup on a 32 band is physically smaller than a D cup on a 38 band, even though both are labeled "D." The letter only indicates the difference between bust and band. This is why sister sizing works. A 34D and a 32DD have the same cup volume, but the 32DD has a tighter, shorter band.

Sizing Tips

• Always start on the loosest hook. New bras should be fastened on the loosest hook to leave room for tightening as the band stretches with wear and washing over the bra's lifespan.
• The band provides 80% of support. A well-fitting band is more important than cup size for comfort and support. If your straps are doing most of the work, your band is too loose.
• Scoop and swoop when putting on a bra. Lean forward, clasp the bra, then use your hands to scoop breast tissue from the sides and underarms into the cups. This ensures all tissue is properly contained and gives you a more accurate sense of whether the cup size is correct.
• Measure at a consistent time. Breast size can fluctuate slightly throughout the menstrual cycle. For the most consistent results, measure at the same point in your cycle each time. Mid-cycle typically gives the most representative measurement.
• Try on multiple sizes. Even with a calculated size, try on your calculated size plus one sister size up and one down. Bra fit is affected by shape, projection, root width, and fabric stretch, none of which are captured by two circumference measurements alone.
• Different styles fit differently. A plunge, balconette, full-cup, and sports bra all fit differently even in the same nominal size from the same brand. Expect some variation and do not assume one size works across all styles.
• Check the center gore. The center piece between the cups (the gore) should sit flat against your sternum. If it lifts away from your body, the cups are too small. If it presses uncomfortably, the cups may be too wide or large for your frame.
• Do the two-finger test. You should be able to slide two fingers under the band comfortably but not more. If you can fit a whole fist, the band is too large. If you cannot fit two fingers, it is too tight.

Bra Style Guide

Different bra styles serve different purposes and work better with specific breast shapes and clothing types. Here is what each common style offers and when to choose it.

When to Replace Your Bras

Bras have a limited lifespan. The elastic in the band and straps degrades with wear, washing, and body heat. Here are the key indicators that a bra needs to be replaced.

• The band stretches to its tightest hook. If you are wearing your bra on the tightest hook and the band still feels loose, the elastic has worn out. A new bra should start on the loosest hook, giving you two more settings as it stretches over time.
• The straps will not stay adjusted. If the strap adjusters slip or the elastic no longer holds tension, the straps cannot support their portion of the load. This usually happens before the band wears out.
• The underwire pokes through. Wire poking through the fabric is a structural failure. Continuing to wear the bra risks skin irritation and poorer support.
• The cups are misshapen. Molded cups that are dented, wrinkled, or warped no longer provide their intended shape. This is often caused by machine washing or drying on high heat.
• General timeline. With regular rotation (3-4 bras in your lineup) and proper care (hand washing or lingerie bag, air drying), a well-made bra lasts about 6-9 months of regular wear. Lower-quality bras may last 3-4 months. If you wear the same bra daily, expect to replace it every 3-4 months regardless of quality.

Bra Care Tips

How you wash and store your bras significantly affects how long they last and how well they maintain their shape.

• Hand wash when possible. Hand washing in cool water with a gentle detergent is the most effective way to preserve bra elastic and shape. Soak for 10-15 minutes, gently agitate, rinse thoroughly, and press out excess water without wringing.
• Use a lingerie bag for machine washing. If you machine wash, always clasp the hooks first (to prevent snagging) and place the bra in a mesh lingerie bag. Use the delicate or hand-wash cycle with cool water.
• Never use a dryer. Heat is the single biggest enemy of bra elastic and molded cups. Always air dry bras by laying them flat or hanging them from the center gore. Do not hang by the straps, as this stretches them out.
• Rotate your bras. Do not wear the same bra two days in a row. The elastic needs 24 hours to recover its shape. Rotating between 3-4 bras extends the life of each one significantly.
• Store flat, not folded. Stack molded-cup bras inside each other like nesting bowls, with cups maintaining their shape. Do not fold one cup into the other, as this creates permanent creases in molded foam cups.

Bra Shopping Guide

Knowing your size is the first step. These practical tips will help you get the best fit when shopping for bras online and in stores.

Shopping In-Store

• Try on at least three sizes. Bring your calculated size, one sister size up, and one sister size down into the fitting room. This accounts for brand variation and helps you find the best fit faster than trying a single size and guessing whether to go up or down.
• Wear a fitted top to the store. After trying on a bra, put your top on over it to see how it looks under actual clothing. Some bras create visible lines, bulging at the band, or an unnatural silhouette that only becomes apparent under clothes.
• Move around in the fitting room. Bend forward, reach overhead, twist side to side. A bra that fits while standing still may shift, ride up, or dig in during normal movement. Test the fit actively, not just while standing with your arms at your sides.
• Ask for a professional fitting. Many department stores and specialty bra retailers offer free fittings by trained staff. Even if you have calculated your size with this tool, a professional can assess your breast shape, root width, and projection, which affect which styles work best for you beyond what measurements can tell you.

Shopping Online

• Check the brand's specific size chart. Do not assume your usual size works across all brands. Each brand publishes their own measurement-to-size conversion chart, and they do differ. A 34C at Victoria's Secret may be a 34D at ThirdLove.
• Read the reviews for sizing feedback. Many online bra reviews include comments like "runs small in the band" or "cups run large." Look for patterns in the reviews to determine whether you should size up or down for a particular style.
• Check the return policy before ordering. Make sure the retailer accepts returns on bras. Some retailers only accept returns on unworn bras with tags attached, while others have more generous try-on policies. Ordering your calculated size plus one sister size and returning what does not fit is a common and effective approach.
• Measure yourself on the same day you order. Do not use a measurement from months ago. Body changes happen gradually and you may not notice until you compare current numbers to previous ones.

Signs of a Fit

When a bra fits correctly, all of these things should be true at the same time:

• The band sits level around your body, parallel to the floor, without riding up in the back.
• The center gore lies flat against your sternum.
• The underwire follows the natural crease of your breast and sits on your ribcage, not on breast tissue.
• The cups contain all breast tissue without overflow at the top, sides, or center.
• The cups lie smooth against the breast without gapping, wrinkling, or empty space.
• The straps stay in place without digging into your shoulders or falling off.
• You can breathe comfortably and move normally without the bra shifting.

Band Size Quick Reference

This table shows the underbust measurement range for each band size across different sizing systems. If your underbust measurement falls between two sizes, try both to see which feels more comfortable.

Cup Size Quick Reference

The cup letter is determined by the difference in inches between your bust measurement and your band size. This table shows how the same difference maps to different cup letters in each sizing system.

Note that US and UK cup sizing align through D but diverge after that point. UK sizing uses double letters (DD, FF, GG, HH) where US sizing skips to the next single letter. EU sizing uses sequential single letters starting from E after D. French and Spanish cup sizing typically follows the EU system.

Common Bra Sizing Myths

Frequently Asked Questions

When Your Size May Change

Bra size is not static. Your measurements may shift during these common life events and transitions. Being aware of when changes are likely helps you know when to remeasure rather than forcing yourself into a size that no longer fits.

A Brief History of Bra Sizing

Understanding where bra sizing came from helps explain why the system works the way it does and why some outdated methods persist.

The modern bra was patented in 1914 by Mary Phelps Jacob. Early bras were sized simply as small, medium, and large. The lettered cup size system was introduced in 1932 by the S.H. Camp and Company, which created A through D cups to classify breast volume. In the 1930s, Maidenform and other manufacturers adopted this system and began combining numbered band sizes with lettered cup sizes.

The "plus 4" method of adding 4 inches to the underbust measurement to determine band size originated during this era. Early bra fabrics had no elastic stretch, so adding inches was necessary to achieve a comfortable fit. As synthetic elastic fabrics became standard in the 1960s through 1980s, the plus-4 method became outdated., some retailers and fitting guides continued to use it well into the 2000s, resulting in widespread incorrect sizing.

Modern fitting methods, popularized by independent bra fitters and online communities in the 2010s, use the direct underbust measurement as the band size without adding inches. This approach, which this calculator uses, produces a snugger band that provides better support and more accurate cup sizing. Studies and surveys consistently show that the majority of bra wearers are in the wrong size, with most wearing a band too large and cups too small.

International sizing systems developed independently in different countries, which is why there is no single universal standard. The US and UK share band numbers but diverge in cup letters after D. The European system uses a completely different band numbering system based on centimeters. French, Spanish, and Italian sizing adds another layer of variation. This calculator handles all five major systems so you can shop from any market.

Detailed Sizing System Differences

Each international sizing system has its own conventions and quirks. Here is a detailed look at how each system works so you can navigate size labels from any country.

US Sizing

The US system uses even-numbered bands (28, 30, 32, 34, etc.) based on your underbust measurement in inches. Cup sizes progress as A, B, C, D, DD, DDD (or F), G, H, I, J, K, L, M, N. The DD and DDD designations are unique to the US system. There is no universal standard enforced by regulation, so brands interpret these sizes with some variation. The US system is used primarily in the United States and Canada.

UK Sizing

The UK system shares the same band numbers as the US (based on inches) but diverges in cup letters after D. The UK progression is A, B, C, D, DD, E, F, FF, G, GG, H, HH, J, JJ, K, KK, L. Note that the UK system uses double letters (FF, GG, HH) instead of advancing to the next single letter. This means a UK F is not the same as a US F. The UK system is considered more standardized than the US system because many UK brands adhere more closely to consistent sizing. Brands like Panache, Fantasie, Freya, and Elomi use UK sizing.

EU Sizing

The European (continental) system uses band numbers based on centimeters, typically in multiples of 5: 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110. These correspond roughly to US/UK 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48. EU cup letters progress sequentially (A, B, C, D, E, F, G, H, I, J) without the double-letter convention used in UK sizing. An EU E cup is equivalent to a US DD.

FR/ES (French and Spanish) Sizing

French and Spanish sizing adds 15 to the US band number (or uses a different centimeter base). A US 32 is an FR 85, US 34 is FR 90, US 36 is FR 95, and so on. Cup letters generally follow the EU convention (sequential single letters). Italian sizing is similar but uses a numbered cup system (1, 2, 3, 4, 5) instead of letters, where Italian 1 corresponds roughly to an A cup.

AU/NZ (Australian and New Zealand) Sizing

Australia and New Zealand use a numbered system that differs from both US and EU numbers. AU band sizes are: 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26. An AU 10 corresponds to a US 32. Cup letters follow the US/UK convention: A, B, C, D, DD, E, F, etc. Some Australian brands follow UK cup progressions, while others follow US progressions, so always check the specific brand's chart.

How Breast Shape Affects Fit

Two people with identical band and bust measurements can need very different bra styles because of differences in breast shape. While this calculator gives you the correct numerical size, understanding your breast shape helps you pick the right style within that size.

Projection

Projection refers to how far the breast extends from the chest wall. Breasts with more projection (sometimes called "projected") stick out further and need deeper cups. Breasts with less projection (sometimes called "shallow") are spread over a wider area and need wider, shallower cups. Molded t-shirt bras work well for shallow shapes. Unlined seamed bras work better for projected shapes because they can accommodate more depth at the apex.

Fullness Distribution

Fullness describes where the majority of breast tissue sits relative to the nipple. Full-on-top shapes have more tissue above the nipple and fill out the upper portion of cups well. Full-on-bottom shapes have more tissue below the nipple and may gap at the top of full-coverage cups. Even fullness sits equally above and below. Balconette bras work well for full-on-bottom shapes. Plunge and full-coverage styles work well for full-on-top shapes.

Root Width

The root is where the breast attaches to the chest wall. Wide roots spread breast tissue across a larger area of the chest. Narrow roots concentrate tissue in a smaller area. This affects which underwire width feels comfortable. Bras with narrow wires will sit on breast tissue (painful) for wide-root shapes. Bras with wide wires will extend too far toward the underarms for narrow-root shapes. Try bras from different brands to find one whose wire width matches your root.

Spacing

The distance between your breasts at the center of your chest affects how the center gore fits. Close-set breasts may find standard gores uncomfortable because the gore sits on breast tissue rather than on the sternum. Plunge bras with narrow, low gores work best for close-set shapes. Wide-set breasts have a clear gap at the center and work well with standard gores.

Measuring Tips for Special Cases

Standard measurement instructions work for most people, but some body types and situations require adjustments for accurate sizing.

Asymmetrical Breasts

It is completely normal for breasts to be slightly different sizes. Studies suggest that more than half of all people have some degree of breast asymmetry. When measuring, use the larger breast for your bust measurement to ensure the cups are large enough. For the smaller breast, you can use a bra insert, removable padding, or choose bras with removable pads where you remove the pad from the larger side. Some specialty bras are specifically for significant asymmetry.

After Breast Surgery

If you have had breast augmentation, reduction, reconstruction, or a mastectomy, standard sizing formulas may not apply perfectly. Implants can change the breast shape and projection in ways that affect which cup styles fit best, even if the numerical measurements align with a standard size. Wait until your surgeon clears you for regular bras (usually 6-12 weeks post-surgery, sometimes longer) and then measure using the standard method. Be prepared to try multiple sizes and styles, as surgical changes may require different bra constructions than what worked before surgery.

During Pregnancy

Breast size changes throughout pregnancy, often increasing by 1-2 cup sizes. The ribcage also expands, which affects band size. Measure yourself at the current point in your pregnancy rather than trying to predict future size changes. Many people go through 2-3 different bra sizes during pregnancy. Stretchy bralettes and wireless nursing bras with flexible sizing can accommodate some fluctuation without needing to be replaced as frequently as structured bras.

While Nursing

Breast size fluctuates throughout the day when breastfeeding, with breasts being larger before feeding and smaller after. Measure when your breasts are moderately full (not immediately before or after a feeding) for the most representative size. Nursing bras with stretch-fabric cups accommodate this daily fluctuation better than molded-cup bras. Drop-down or pull-aside cup styles provide practical access for feeding.

Larger Band Sizes (40+)

People with larger band sizes may find that standard measurement methods underestimate band size because soft tissue around the ribcage compresses differently. If your initial calculated size feels too tight, try one band size up with the same cup letter. Many extended-size brands (Elomi, Goddess, Glamorise) have slightly different fit characteristics than standard-size brands, so try multiple brands to find the best fit.

Smaller Band Sizes (Below 30)

Band sizes below 30 are less commonly stocked in retail stores, which makes finding bras more challenging. UK brands tend to offer the widest range of small band sizes, with Panache, Freya, and Comexim going down to 26 and 28 bands in many styles. When measuring for small bands, accuracy is especially important because even a 1-inch discrepancy represents a larger proportional error on a small band compared to a large one.

Bra Sizing by the Numbers

These statistics from industry surveys and fitting studies put bra sizing in broader context.

• 80% of bra wearers are in the wrong size according to multiple studies conducted by lingerie retailers and researchers. The most common error is wearing a band that is too large and cups that are too small.
• The average US bra size has increased from 34B to 34DD over the past two decades, according to industry data. This is attributed to a combination of better fitting awareness (people finding their correct size instead of defaulting to B/C cups), changes in average body size, and expanded size ranges from manufacturers.
• The average bra lasts 6-9 months with proper care and rotation. Most people do not replace bras often enough, wearing them well past the point where the elastic has degraded and support has diminished.
• A well-fitting bra has the band provide 80% of support, the cups provide 10%, and the straps provide 10%. This is why band fit is the single most important factor in bra sizing, and why a too-loose band cannot be compensated by tightening the straps.
• Breast size can vary by half to a full cup throughout the menstrual cycle due to hormonal fluid retention, according to breast health research. This is a normal physiological variation, not a sizing error.

About This Calculator

This bra size calculator was provide accurate, stigma-free sizing information for anyone who needs it. Bra sizing should be straightforward, but the combination of multiple international systems, outdated fitting methods still in circulation, and brand-to-brand variation makes it unnecessarily confusing.

This tool uses the modern fitting method of taking the underbust measurement directly as the band size (rounded to the nearest even number) without adding inches. This approach, endorsed by professional bra fitters and independent fitting communities worldwide, produces more accurate results than the outdated plus-4 method that some retailers still use.

The calculator covers five international sizing systems (US, UK, EU, FR/ES, AU/NZ), generates sister sizes for fit troubleshooting, and provides context through the measurement guide, fit issues section, and style recommendations. All calculations run entirely in your browser with no data sent to any server.

For specialized fitting needs such as post-surgical sizing, fitting for significant asymmetry, or finding bras for very small or very large band sizes, I recommend consulting with a professional bra fitter who can assess shape and fit factors that measurements alone cannot capture. This calculator gives you an excellent starting point, but in-person fitting adds an additional layer of precision for complex sizing situations.

Bra Fitting Glossary

Common terms you will encounter when researching bra fit. Understanding this vocabulary helps you describe fit issues accurately when seeking help from fitters or online communities.

• The horizontal fabric strip that wraps around your ribcage below the bust. Provides the majority of a bra's support.
• The center piece of fabric or wire channel between the two cups. Should sit flat against the sternum in a well-fitting bra.
• A U-shaped wire that follows the base of the breast to provide structure and shape. Should sit on the ribcage, not on breast tissue.
• The side panel of the bra that extends from the cup to the closure. Wider wings provide more lateral support and a smoother silhouette.
• Another term for the center gore, specifically the section that connects the two cups.
• A bra size with the same cup volume as another but a different band size. For example, 34C, 32D, and 36B are sister sizes.
• How far the breast extends from the chest wall. Affects which cup shapes and depths work best.
• The area where the breast tissue attaches to the chest wall. Can be narrow or wide, tall or short.
• Quad-boob: Informal term for breast tissue spilling over the top edge of the cup, creating four visible mounds instead of two. Indicates cups are too small.
• The technique of reaching into the cup to pull all breast tissue forward and into the cup when putting on a bra.
• Whether the center gore sits flat against the sternum. "The gore tacks" means it sits flush; "the gore floats" means it lifts away, indicating cups too small.
• IMF (Inframammary Fold): The crease where the underside of the breast meets the chest wall. The underwire should sit in or near this fold.

Bra Fitting Checklist

Use this checklist every time you try on a bra to evaluate whether it fits correctly. All items should pass for a proper fit.

References

1. ThirdLove Bra Fit Guide - ThirdLove, Inc. Detailed fit guide with sizing methodology, measurement instructions, and half-size cup information.
2. Bratabase - Crowdsourced bra measurement database with detailed measurements and fit reports across hundreds of brands and thousands of styles.
3. ASTM D5585 Standard Table of Body Measurements - ASTM International. Industry-standard body measurement data used for apparel sizing in the United States.

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