How Do I Calculate My Bra Size

Measure your perfect fit in just 3 simple steps

Complete Guide: How to Calculate Your Bra Size Accurately

Finding the perfect bra size is essential for comfort, support, and overall breast health. Studies show that 80% of women wear the wrong bra size, which can lead to discomfort, poor posture, and even long-term health issues. This comprehensive guide will walk you through the professional measurement process, common fitting mistakes, and expert tips for finding your ideal bra size.

Why Bra Size Matters

Wearing the correct bra size provides numerous benefits:

• Improved posture – Proper support reduces strain on your back and shoulders
• Enhanced comfort – No more digging straps or riding-up bands
• Better breast health – Proper support can prevent ligament damage over time
• Confidence boost – A well-fitted bra enhances your natural shape
• Clothing fit – Your clothes will drape better over a properly supported bust

The Science Behind Bra Sizing

Bra sizes are determined by two primary measurements:

1. Band size – The number (e.g., 32, 34, 36) representing your ribcage measurement
2. Cup size – The letter (e.g., A, B, C, D) representing the difference between your bust and band measurements

Measurement Difference (inches)	US/UK Cup Size	European Cup Size	French Cup Size
0″	AA	AA	AA
1″	A	A	A
2″	B	B	B
3″	C	C	C
4″	D	D	D
5″	DD/E	E	E
6″	DDD/F	F	F
7″	G	G	G
8″	H	H	H
9″	I	I	I
10″	J	J	J

Step-by-Step Measurement Guide

1. Measure Your Band Size

Stand upright without a bra or wearing a non-padded bra. Use a soft measuring tape to measure:

• Directly under your bust (where the bra band sits)
• Keep the tape snug but not tight
• Ensure the tape is parallel to the floor
• Round to the nearest whole number if you get a fraction

Pro Tip: If the measurement is even, this is your band size. If odd, add 1 inch (for US sizing) to get your band size.

2. Measure Your Bust Size

While still wearing a non-padded bra (or no bra), measure:

• Around the fullest part of your bust
• Keep the tape parallel to the floor
• Don’t pull the tape too tight – it should graze your bust without compressing
• Note the measurement in inches

3. Calculate Your Cup Size

Subtract your band measurement from your bust measurement:

• 1″ difference = A cup
• 2″ difference = B cup
• 3″ difference = C cup
• 4″ difference = D cup
• 5″ difference = DD/E cup
• And so on…

Common Bra Fitting Mistakes

Problem	Cause	Solution
Band rides up	Band is too large	Go down a band size, up a cup size
Straps dig in	Band is too large, carrying the weight	Tighten band, loosen straps
Cup gaping	Cup is too large	Go down a cup size
Spillage over cups	Cup is too small	Go up a cup size
Underwire digs	Cup is too small or wrong shape	Try a larger cup or different style
Center doesn’t lie flat	Cup is too small	Go up a cup size

Understanding Sister Sizes

Sister sizes are alternative sizes that have the same cup volume but different band sizes. For example:

• 34C and 32D are sister sizes (same cup volume, different band sizes)
• 36B and 34C are sister sizes
• 30E and 32DD are sister sizes

Sister sizes can be useful when:

• Your exact size isn’t available
• You prefer a tighter or looser band
• You’re between sizes

Bra Size Variations by Country

Bra sizing systems vary internationally. Here’s a quick reference:

• US/UK: Band size + cup letter (34C)
• European: Band size in cm + cup letter (75C)
• French: Band size in cm + cup letter (90C – note: French bands run larger)
• Australian: Same as UK but with different band sizing (10C = UK 32C)
• Japanese: Band in cm + cup size based on cm difference

When to Get Professionally Fitted

While our calculator provides excellent results, consider a professional fitting if:

• You’ve had significant weight changes
• You’re pregnant or breastfeeding
• You’ve had breast surgery
• You experience chronic discomfort in bras
• You’re buying expensive bras (£50+)

Many department stores and lingerie boutiques offer free fitting services. Some specialty stores even use 3D scanning technology for precise measurements.

Bra Care and Longevity

To maintain your bras and ensure accurate sizing over time:

• Hand wash bras in cool water with mild detergent
• Fastener hooks when washing to prevent snagging
• Air dry flat – never put bras in the dryer
• Rotate between 3-5 bras to extend their life
• Replace bras every 6-12 months or when they lose support

Expert Resources

For more authoritative information on bra fitting and breast health:

• National Cancer Institute – Breast Health Information
• Office on Women’s Health – Breast Health Guide
• MedlinePlus – Breast Diseases and Conditions

Frequently Asked Questions

How often should I measure my bra size?

You should check your bra size every 6 months, or whenever you notice:

• Weight fluctuations of 10+ pounds
• Pregnancy or breastfeeding
• Hormonal changes (puberty, menopause)
• Discomfort in your current bras

Why do my bras feel different in different brands?

Bra sizing isn’t standardized across brands. Factors that affect fit include:

• Band elasticity (some brands run tighter)
• Cup shape (shallow vs. projected)
• Fabric composition
• Country of origin (different sizing systems)
• Style differences (sports bras vs. lace bras)

Always try bras on when possible, and don’t be afraid to size up or down within the same brand.

Can I measure myself accurately at home?

Yes! With proper technique, self-measurement can be just as accurate as professional fitting. Key tips:

• Use a soft, flexible measuring tape
• Measure while standing straight (no slouching)
• Wear a non-padded bra or no bra
• Take measurements 2-3 times for consistency
• Measure at the end of the day when you’re slightly larger

What if I’m between sizes?

If your measurements fall between sizes:

• For band size: Size up if you prefer comfort, down if you prefer support
• For cup size: Try both sizes to see which fits better
• Consider sister sizes for alternative fits
• Look for bras with adjustable bands and straps

Final Tips for Bra Shopping

• Always try bras on before purchasing when possible
• Fastener new bras on the loosest hook – they’ll stretch over time
• The band should provide 80% of the support, straps only 20%
• Your breasts should be fully encased in the cups with no spillage
• The center gore (between cups) should lie flat against your sternum
• Move around in the fitting room – jump, bend, and stretch to test support