How do I measure my bra size accurately?

To measure your bra size accurately: 1) Wear a non-padded, well-fitting bra. 2) Measure band size: Use a soft measuring tape directly under your bust, keeping it snug but not tight. Round to the nearest whole number; if odd, add 1 to get an even number. 3) Measure bust size: Measure around the fullest part of your bust, keeping the tape parallel to the ground. 4) Calculate cup size: Subtract band size from bust size. Each inch of difference equals one cup size (1" = A, 2" = B, 3" = C, etc.). For example, if your underbust is 34 inches and bust is 37 inches, the difference is 3 inches, making you a 34C. Measure at the same time of day and avoid measuring during menstruation when breast size may fluctuate.

What are sister sizes and when should I use them?

Sister sizes are bra sizes with the same cup volume but different band sizes. When you go down one band size, you go up one cup size (and vice versa) to maintain the same cup volume. For example, 34C, 32D, and 36B are sister sizes. Use sister sizes when: your calculated size is unavailable, the band feels too tight or too loose, you're between sizes, or you want a different fit preference. If 34C feels too loose in the band, try 32D (tighter band, same cup volume). If too tight, try 36B (looser band, same volume). Sister sizes are particularly helpful with different bra styles and brands that fit differently. However, they're alternatives, not exact matches - always try them on to ensure proper fit.

How do bra sizes differ between countries?

Bra sizing systems vary significantly by country. US and UK use inches for band size, with similar sizing but UK DD is US D (UK uses double letters more). EU and FR use centimeters: EU adds approximately 10-15cm to underbust measurement, while FR adds about 15cm. Australia generally follows US sizing. Japan uses underbust in cm plus 65 for band size. For example, a US 34C converts to: UK 34C (same), EU 75C (34 inches × 2.54 + 10 ≈ 75cm), FR 90C (34 × 2.54 + 15 ≈ 90cm), AU 12C or 34C, JP 75C (similar to EU). Cup progression also varies: while US goes A, B, C, D, DD/E, UK may use DD, E, F where US uses DD, DDD/F, G. Always check brand-specific size charts as sizing can vary even within the same country.

Why doesn't my calculated size fit properly?

Several factors affect bra fit beyond calculations: 1) Brand variation - sizing isn't standardized; different brands fit differently even in the same size. 2) Bra style - push-up, balconette, full-coverage, sports, and wireless bras all fit differently. 3) Breast shape - affects fit as much as size. Breasts can be shallow, projected, wide-set, close-set, full-on-top, or full-on-bottom. 4) Tissue firmness - affects how cups fill. 5) Measurement timing - breast size fluctuates with menstrual cycle, weight changes, and age. 6) Measurement errors - incorrect tape placement or tension. 7) Wearing the wrong size previously - breast tissue may have migrated; proper fitting can correct this over time. If calculated size doesn't fit: try sister sizes, consult professional fitters, try multiple brands, and remember that calculator results are starting points, not guarantees.

How often should I measure and update my bra size?

Measure your bra size: every 6-12 months as a routine check, after weight changes of 10+ pounds (5+ kg), after pregnancy and breastfeeding, during adolescence (every 6 months), during menopause when hormone changes affect breast tissue, if your current bras feel uncomfortable, if you notice fit issues (spillage, gaps, band riding up), and when starting a new fitness regimen. Signs you need remeasuring: band rides up in back, straps constantly slip off, spillage over cups, gaps in cups, underwire pokes or digs in, you're constantly adjusting your bra, or back and shoulder pain. Breast size naturally fluctuates with menstrual cycle, so measure mid-cycle for most accurate results. Many women wear the wrong size for years - studies show 80% of women wear incorrect bra sizes. Regular measuring ensures optimal fit, comfort, and support.

What are the signs of a properly fitting bra?

A properly fitting bra has these characteristics: 1) Band: Fits snugly around ribcage on loosest hook (allowing for stretching over time), stays level around body without riding up, and you can fit two fingers under band but it shouldn't move more than 1 inch when pulled. 2) Cups: Fully contain breasts with no spillage over top or sides, no gaps or wrinkling in fabric, underwire (if present) follows natural breast crease without poking or pinching, and center gore (between cups) lies flat against sternum. 3) Straps: Stay in place without slipping, don't dig into shoulders, bear only 10-20% of breast weight (band should support 80-90%). 4) Overall comfort: Can wear all day without discomfort, allows full range of motion, doesn't require constant adjusting, and breasts feel supported without pain. If any element is off, try different sizes or styles.

Bra Size Calculator & Converter - Find Your Perfect Fit | AICalculator

The Complete Guide to Finding Your Perfect Bra Size

Finding the right bra size is essential 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. This comprehensive guide will help you measure accurately, understand sizing systems, and find your perfect fit.

Understanding Bra Sizing

Bra sizes consist of two components: the band size (number) and the cup size (letter). The band size represents the circumference of your ribcage directly under your bust, while the cup size represents the volume of your breasts based on the difference between your bust and band measurements.

For example, in size 34C, "34" is the band size in inches (the measurement around your ribcage under your bust), and "C" is the cup size (indicating a 3-inch difference between bust and band measurements). Understanding this system is the first step to finding your perfect fit.

How to Measure Your Bra Size

What You'll Need

Soft measuring tape: Cloth or soft plastic, not rigid metal
Mirror: Full-length or large enough to see your torso
Non-padded bra: Your best-fitting current bra
Helper (optional): Makes measurement easier and more accurate

Step-by-Step Measurement Guide

Step 1: Measure Band Size

1.Stand straight with arms relaxed at your sides
2.Wrap the tape around your ribcage directly under your bust (underbust)
3.Keep the tape level and parallel to the ground
4.The tape should be snug but not tight - you should be able to fit two fingers underneath
5.Breathe normally and take the measurement
6.Round to the nearest whole number; if odd, add 1 (band sizes are even)

Step 2: Measure Bust Size

1.Wear your best-fitting, non-padded bra
2.Wrap the tape around the fullest part of your bust (typically at nipple level)
3.Keep the tape level and parallel to the ground
4.Don't pull the tape too tight - it should lie flat without compressing breast tissue
5.Stand straight with arms at your sides
6.Record the measurement to the nearest quarter inch or half centimeter

Cup Size Calculation

Cup size is determined by the difference between your bust and band measurements:

Difference	Cup Size	Example
Less than 1"	AA	Band 34" + Bust 34.5" = 34AA
1 inch (2.5 cm)	A	Band 34" + Bust 35" = 34A
2 inches (5 cm)	B	Band 34" + Bust 36" = 34B
3 inches (7.5 cm)	C	Band 34" + Bust 37" = 34C
4 inches (10 cm)	D	Band 34" + Bust 38" = 34D
5 inches (12.5 cm)	DD/E	Band 34" + Bust 39" = 34DD
6 inches (15 cm)	DDD/F	Band 34" + Bust 40" = 34DDD
7+ inches (17.5+ cm)	G, H, I, J, K...	Continue alphabet progression

International Bra Size Conversions

Bra sizing systems vary significantly between countries. Here's how to convert between major sizing systems:

US	UK	EU	FR	AU	JP
30B	30B	65B	80B	8B/30B	65B
32C	32C	70C	85C	10C/32C	70C
34C	34C	75C	90C	12C/34C	75C
36D	36D	80D	95D	14D/36D	80D
38DD	38DD	85E	100E	16DD/38DD	85E

Understanding Sister Sizes

Sister sizes are alternative bra sizes that have the same cup volume but different band sizes. This concept is incredibly useful when your calculated size is unavailable or when you're between sizes.

How Sister Sizes Work

When you decrease the band size by one (2 inches), you increase the cup size by one letter to maintain the same cup volume. Conversely, when you increase the band size, you decrease the cup size. For example:

Sister Size Examples:

32D↔34C↔36B

30DD↔32D↔34C

34B↔36A↔38AA

When to Use Sister Sizes

Size unavailable: When your calculated size is out of stock
Band too tight: Go up one band size and down one cup size
Band too loose: Go down one band size and up one cup size
Between sizes: Try sister sizes to find the best fit
Brand variations: Different brands fit differently; sister sizes provide options
Style differences: Different bra styles (push-up, sports, wireless) may require sister sizes

Signs of a Perfect Fit

A properly fitting bra should be comfortable all day and provide adequate support. Here's what to look for:

✓ Good Fit Indicators

• Band stays level around body
• Band fits snugly on loosest hook
• Cups contain breasts fully
• No spillage or gaps
• Center gore lies flat
• Underwire follows breast crease
• Straps stay in place
• Comfortable all day
• Can move freely
• Minimal adjusting needed

✗ Poor Fit Warning Signs

• Band rides up in back
• Band is too tight or loose
• Breast tissue spills over cups
• Gaps or wrinkling in cups
• Center gore doesn't touch skin
• Underwire pokes or digs
• Straps slip off or dig in
• Uncomfortable or painful
• Constantly need to adjust
• Back or shoulder pain

Common Bra Fitting Mistakes

Mistake 1: Wearing the Wrong Band Size

Problem: Many women wear bands that are too large, relying on straps for support. The band should provide 80-90% of breast support.
Solution: Ensure band is snug on loosest hook. If it rides up or moves more than 1 inch when pulled, it's too loose.

Mistake 2: Assuming Cup Size is Static

Problem: Cup size is relative to band size. A 32D has smaller cups than a 38D, though both are "D cups."
Solution: Always consider band and cup size together. Understand sister sizes for accurate fit across different band sizes.

Mistake 3: Not Adjusting for Brand Differences

Problem: Bra sizing isn't standardized. Different brands fit differently even in the same size.
Solution: Always try on bras before buying. Keep notes on which brands run large, small, or true to size for your body.

Mistake 4: Ignoring Breast Shape

Problem: Breast shape (shallow, projected, wide-set, close-set) affects fit as much as size.
Solution: Try different bra styles. Balconette, plunge, full-coverage, and demi bras suit different breast shapes.

Bra Styles and When to Wear Them

T-Shirt / Seamless Bra

Best For: Everyday wear, fitted clothing

Smooth cups create a seamless look under clothing. Molded or lightly padded cups prevent show-through.

Full-Coverage / Support Bra

Best For: Larger busts, all-day support

Covers entire breast, provides maximum support and containment. Often features wide straps and reinforced band.

Push-Up / Padded Bra

Best For: Adding volume, enhancing cleavage

Padding at bottom of cups lifts breasts. Creates fuller appearance and enhances décolletage.

Balconette / Demi Bra

Best For: V-neck, scoop-neck tops

Lower cut with wider-set straps. Shows more cleavage while providing good support. Great for low necklines.

Sports Bra

Best For: Exercise, high-impact activities

Minimizes breast movement during physical activity. Compression or encapsulation styles available.

Wireless / Bralette

Best For: Comfort, lounging, smaller busts

No underwire for maximum comfort. Softer support, great for home wear and smaller cup sizes.

Caring for Your Bras

Proper care extends bra lifespan and maintains shape and support:

Washing and Drying

Hand wash preferred: Use lukewarm water and gentle detergent. Swish and squeeze gently, don't wring
Machine wash (if necessary): Use lingerie bag, gentle cycle, cold water, and hook bras closed
Air dry only: Never machine dry. Heat damages elastic and shape. Lay flat or hang by center gore
Wash frequency: After 2-3 wears, or after sweating. Rotate bras to avoid wearing same one consecutively

Storage

Keep shape: Never fold cups. Stack bras or lay flat in drawer
Organize: Store by type or frequency of use for easy access
Protect: Keep away from rough fabrics that can snag delicate materials

When to Replace

Every 6-12 months: Regular wear stretches elastic and reduces support
Signs to replace: Band no longer fits on tightest hook, cups lose shape, underwire pokes through, straps lose elasticity
Rotate collection: Own 3-5 everyday bras to extend lifespan of each

Professional Bra Fitting

While this calculator provides accurate estimates, professional fitting is highly recommended:

Benefits of Professional Fitting:

• Expert assessment of breast shape and tissue distribution
• Personalized recommendations for styles that suit your body
• Adjustment guidance and fit troubleshooting
• Access to wide range of sizes including hard-to-find options
• Brand-specific knowledge and sizing variations

Consider professional fitting if you're pregnant, nursing, experiencing weight changes, post-surgery, or simply can't find a comfortable fit. Many lingerie stores and department stores offer free fitting services.

Resources and Further Information

For additional information on bra fitting and sizing:

Bra Size Calculator - Find Your Perfect Fit with Size Conversions