Our precision bra size calculator helps you determine your ideal bra size based on your unique measurements. Finding the right fit is essential for comfort, support, and confidence. This calculator provides results for the United States, United Kingdom, European Union, France, Belgium, Spain, Australia, and New Zealand sizing systems.
The bust size is the loose circumference measured around the chest over the fullest part of the breasts, while standing straight with arms to the side, and wearing a properly fitted bra.
The band or frame size is the firm circumference, fitted not tightly, measured directly underneath the breasts.
Use the converter below to translate your bra size between different international sizing systems.
Finding your correct bra size is essential for comfort, support, and confidence. Follow these steps to measure yourself accurately:
Using a soft measuring tape, measure around your ribcage just under your breasts. The tape should be snug but not tight. Round to the nearest whole number. If the number is even, add 4 inches. If it's odd, add 5 inches. This is your band size. (Note: Some modern fitting methods skip the adding of inches - our calculator accommodates both approaches.)
Measure around the fullest part of your bust while wearing a non-padded bra. Keep the tape level and somewhat loose. Round to the nearest whole number.
Subtract your band size from your bust measurement. The difference determines your cup size according to the following chart:
| Difference (inches) | US Cup Size | UK Cup Size |
|---|---|---|
| Less than 1" | AA | AA |
| 1" | A | A |
| 2" | B | B |
| 3" | C | C |
| 4" | D | D |
| 5" | DD/E | DD |
| 6" | DDD/F | E |
| 7" | G | F |
| 8" | H | FF |
| 9" | I | G |
| 10" | J | GG |
Bra sizing varies significantly around the world, making international shopping challenging. Here's a comprehensive overview of the major sizing systems:
| Size Category | FR/BE/ES | EU (EN 13402) | US and UK | AU, NZ |
|---|---|---|---|---|
| XXS | 75 | 60 | 28 | 6 |
| XS | 80 | 65 | 30 | 8 |
| S | 85 | 70 | 32 | 10 |
| M | 90 | 75 | 34 | 12 |
| L | 95 | 80 | 36 | 14 |
| XL | 100 | 85 | 38 | 16 |
| XXL | 105 | 90 | 40 | 18 |
Studies indicate that approximately 80% of women wear incorrectly sized bras, which can lead to numerous issues including:
Wearing the correct bra size provides proper support, enhances your natural shape, improves posture, increases comfort, and can make your clothes fit better.
You may be wearing the wrong bra size if you experience any of these common issues:
The modern bra sizing system has evolved significantly since its inception in the early 20th century. Understanding the science behind proper bra fit can help you make better choices for your comfort and health.
Breasts are primarily supported by Cooper's ligaments, which are connective tissue that can stretch permanently without proper support. A well-fitted bra helps distribute weight evenly across the shoulders, back, and chest, reducing strain on these ligaments and surrounding tissues.
The distribution of breast tissue varies significantly between individuals. Some women have more tissue toward the center, sides, top, or bottom of the breast. This variation is why different bra styles work better for different breast shapes, even within the same size.
From a physics perspective, a properly fitted bra works by:
Research in biomechanics has shown that unsupported breasts can move up to 15cm during physical activity, potentially causing discomfort and tissue damage. This movement occurs in three dimensions: up-down, side-to-side, and forward-back.
A 2013 study published in the Journal of Biomechanics found that breast pain and discomfort during exercise is directly related to the amount of breast movement, particularly vertical displacement. This research underscores the importance of proper support, especially for high-impact activities.
The history of bra sizing reflects changing attitudes toward women's bodies, fashion trends, and advancements in textile technology.
The first commercial standardized cup sizing was introduced in the 1930s by S.H. Camp and Company, which correlated breast sizes with letters of the alphabet (A, B, C, D). Before this innovation, bras were sized similar to clothing with small, medium, and large designations.
In the 1940s and 1950s, as bra manufacturing became more sophisticated, additional cup sizes were added to accommodate a wider range of body types. The DD cup was introduced in the 1950s, with further expansions in subsequent decades.
The 1970s saw a shift toward more natural silhouettes and the introduction of the first sports bras. By the 1990s, specialized sizing for fuller figures became more widely available, and the 2000s brought innovations in measurement techniques and size inclusivity.
Today, many specialty brands offer cup sizes ranging from AA to N and beyond, reflecting a more inclusive approach to body diversity. The traditional method of adding 4-5 inches to the underbust measurement has been challenged by modern fitting methods that often use the actual underbust measurement as the band size.
Technology has also transformed bra fitting, with 3D body scanning, AI-powered sizing recommendations, and custom-fitted bras becoming increasingly accessible. These innovations aim to address the limitations of standardized sizing systems and provide more personalized fit solutions.
This outdated method dates back to when bra materials lacked elasticity. Modern bras are made with stretchier fabrics, making this addition unnecessary and often resulting in bands that are too loose. Many professional fitters now recommend using the actual underbust measurement as the starting point.
Cup size is relative to band size, not an absolute volume. For example, a 34C has the same cup volume as a 36B or a 32D. This relationship is known as "sister sizing" and is useful when adjusting for comfort while maintaining the same cup volume.
Cup size alone doesn't indicate breast size—it represents the difference between bust and band measurements. A properly fitted D cup on a small frame may appear quite different from a D cup on a larger frame.
New bras should fit comfortably on the loosest hook, allowing you to tighten the band as the elastic naturally stretches over time, extending the garment's lifespan.
Different bra styles are designed to fit differently. A plunge bra, balconette, full-coverage, and sports bra may all fit the same person but in different sizes due to their construction and purpose.
Different bra styles serve various purposes and may require specific sizing considerations:
These provide additional support during physical activity and often use compression, encapsulation, or a combination of both. Many sports bras use simplified sizing (S, M, L) or may require sizing up or down from your regular bra size depending on the level of compression.
Designed for breastfeeding mothers, these typically feature cups that can be easily unclasped. Experts recommend being fitted during the eighth month of pregnancy and again a few weeks postpartum as breast size fluctuates significantly during this period.
These specialized bras include pockets to hold breast prostheses after mastectomy surgery. Proper fitting is crucial for comfort and symmetry, and is best done by specialists trained in post-mastectomy fitting.
Designed to reduce the projected profile of larger breasts, these redistribute breast tissue to create a smaller silhouette. They may require a different size than your standard bra.
These enhance cleavage and lift through padding or specially designed cups. The added volume from padding may require adjusting cup size compared to non-padded styles.
The bra industry is evolving with new technologies and approaches to sizing:
Bra preferences and sizing systems vary significantly across different cultures and regions, reflecting diverse beauty standards, fashion trends, and practical considerations.
In Japan, Korea, and China, smaller cup sizes and push-up styles are often preferred. Japanese sizing typically runs smaller than Western sizing, with bands measured in centimeters and cups using letters. The Japanese market also features innovative materials and designs, including air-filled pads and cooling fabrics for comfort in humid climates.
European countries tend to emphasize natural silhouettes and high-quality materials. French lingerie is renowned for its craftsmanship and aesthetic appeal, while Scandinavian brands often focus on comfort and practicality. European sizing systems vary, with France and Spain using centimeter measurements that are 15cm larger than the actual underbust measurement.
The United States and Canada have seen a growing emphasis on size inclusivity, with many brands expanding their size ranges to accommodate more body types. There's also been a shift toward wireless bras and bralettes, reflecting changing priorities around comfort versus traditional structured support.
Different regions show distinct preferences in bra fit and style:
These cultural variations highlight the importance of understanding regional sizing systems when shopping internationally for lingerie.
The impact of bra fit extends beyond comfort to affect various aspects of physical health:
A 2018 study published in the Journal of Orthopaedic & Sports Physical Therapy found that properly fitted bras can significantly improve posture in women with larger breasts. The research demonstrated reduced forward shoulder positioning and decreased thoracic kyphosis (upper back rounding) when appropriate support was provided.
Conversely, insufficient support can lead to compensatory posture changes, including forward head position, rounded shoulders, and increased lumbar lordosis (swayback). These postural adaptations can contribute to chronic pain conditions affecting the neck, shoulders, and back.
Ill-fitting bras can cause various skin issues, including:
Proper fit minimizes these risks by reducing friction and pressure while allowing adequate airflow to keep skin dry.
While no scientific evidence suggests that bras cause or prevent breast cancer, proper support is important for breast health. Research from the University of Portsmouth's Research Group in Breast Health has shown that unsupported breast movement during exercise can lead to micro-tears in Cooper's ligaments, potentially contributing to premature sagging.
For women who have undergone breast surgery, appropriate support is crucial for healing and comfort. Specialized post-surgical and mastectomy bras are designed to accommodate specific needs during recovery and beyond.
I've been wearing the wrong size for years! This calculator helped me find my true size, and the international conversion is so helpful for online shopping. The detailed explanations about fit issues were eye-opening.
As a professional bra fitter, I recommend this calculator to clients who want to check their size at home. It's one of the most accurate online tools I've found, especially since it accounts for both traditional and modern sizing methods.
After pregnancy and breastfeeding, my size changed completely. This calculator helped me find my new size without the awkwardness of in-store fittings. The educational content about nursing bras was particularly helpful.
I shop for lingerie internationally and this calculator has saved me so much hassle with size conversions. The only improvement I'd suggest is adding more Asian sizing systems, but it's still the best converter I've found online.
As someone who recently had breast reduction surgery, finding my new size was challenging. This calculator gave me an accurate starting point, and the information about post-surgical bras was invaluable during my recovery.
A properly fitting bra should meet these criteria:
If your bra doesn't meet these criteria, you likely need a different size or style.
It's recommended to measure your bra size every 6-12 months, as body changes can affect your fit. You should definitely remeasure after significant weight changes (gain or loss of 5-10 pounds), pregnancy, breastfeeding, hormonal changes, menopause, or any breast surgery. Many women's sizes fluctuate throughout their lives, so regular measurement ensures optimal comfort and support.
Sister sizing refers to bra sizes that have the same cup volume but different band/cup combinations. When you go up a band size, you need to go down a cup size to maintain the same volume (and vice versa). For example, sister sizes to a 34C would include 32D and 36B.
This concept is useful when the cup volume is correct but the band feels too tight or loose. Sister sizing allows you to adjust the band size while maintaining the same cup volume. However, sister sizing works best within one size up or down, as the cup shape and proportions change more dramatically with larger adjustments.
Bra sizes vary between brands due to several factors:
This variation means you might wear different sizes across different brands. It's helpful to try on bras or check size charts specific to each manufacturer.
The practice of adding 4-5 inches to the underbust measurement (also called the "+4 method") is traditional but increasingly considered outdated. This method originated when bra materials had little stretch, but modern bras use more elastic fabrics.
Many modern fitting specialists recommend using your actual underbust measurement (rounded to the nearest even number) as your band size. However, some women find this too tight and prefer adding 2 inches instead of 4.
Our calculator provides results using both methods, allowing you to compare and decide which feels more comfortable. The most important factor is how the bra actually fits and feels on your body, regardless of the number on the label.
Converting between sizing systems can be complex, especially for larger cup sizes where the progression differs. Here's a simplified guide:
For the most accurate conversions, use our bra size converter tool above, which accounts for these complex relationships.
Proper bra care extends the life of your garments and maintains their supportive properties:
With proper care, a quality bra should last approximately 6-9 months of regular wear before the elastic begins to degrade significantly.
Different breast shapes benefit from different bra styles:
Remember that breast shape is distinct from size, and finding the right style is often as important as finding the right size for optimal comfort and appearance.
Yes, consistently wearing ill-fitting bras can contribute to several health issues:
Research from the University of Portsmouth found that up to 70% of women report at least one of these issues related to poor bra fit. Finding the correct size and style can alleviate many of these problems.
When selecting a sports bra, consider these factors:
Research from the University of Portsmouth's Research Group in Breast Health found that unsupported breasts can move up to 15cm during running, potentially causing pain and tissue damage. A properly fitted sports bra can reduce this movement by up to 85%.
Finding your correct bra size is a crucial step toward improved comfort, support, and confidence. Our bra size calculator provides a reliable starting point, but remember that individual preferences, body shapes, and brand variations may require some adjustment.
The perfect fit combines the right measurements with the appropriate style for your unique body shape and lifestyle needs. Don't hesitate to try different sizes and styles until you find what works best for you.
For the most accurate fit, consider combining the results from our calculator with a professional fitting, especially if you're experiencing significant discomfort with your current bras or have recently undergone body changes like pregnancy, weight fluctuation, or surgery.
Remember that bra sizing is not standardized across brands, so your size may vary between manufacturers. The most important factor is how the bra feels and functions on your body, regardless of the number or letter on the label.
