How To Calculate My Cup Size

Measure your perfect fit in just 3 simple steps. Get accurate results based on professional sizing standards.

Comprehensive Guide: How to Calculate Your Cup Size Accurately

Finding the perfect bra size is essential for both comfort and health. Wearing the wrong bra size can lead to back pain, poor posture, and even breathing difficulties. This comprehensive guide will walk you through everything you need to know about calculating your cup size correctly.

The Science Behind Bra Sizing

Bra sizes are determined by two primary measurements:

1. Band size: The measurement around your ribcage, directly under your bust
2. Cup size: The difference between your bust measurement and band size

The band size typically ranges from 28 to 50+ in even numbers (in inches), while cup sizes progress alphabetically (AA, A, B, C, etc.) with each letter representing approximately 1 inch of difference between bust and band measurements.

Step-by-Step Measurement Process

1. Measuring Your Band Size

Follow these steps for accurate band measurement:

• Stand upright without a bra or wear a non-padded bra
• Use a soft measuring tape (not a metal one)
• Measure snugly around your ribcage, directly under your bust
• Keep the tape parallel to the floor
• Ensure the tape is snug but not tight (you should be able to slide one finger underneath)
• Exhale normally and record the measurement

Underbust Measurement (inches)	Band Size (US)	Band Size (UK/EU)
26-27	28	60
28-29	30	65
30-31	32	70
32-33	34	75
34-35	36	80
36-37	38	85
38-39	40	90
40-41	42	95
42-43	44	100
44-45	46	105

2. Measuring Your Bust Size

For accurate bust measurement:

• Stand with your arms at your sides
• Measure around the fullest part of your bust (usually over the nipples)
• Keep the tape parallel to the floor
• Don’t pull the tape too tight – it should graze your skin
• Record the measurement while standing straight

3. Calculating Your Cup Size

The cup size is determined by the difference between your bust measurement and band size:

Difference (inches)	US Cup Size	UK/EU Cup Size
0	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

Common Bra Fitting Mistakes to Avoid

• Measuring over clothes: Always measure directly against your skin or a non-padded bra for accuracy
• Pulling the tape too tight: This can give you a smaller (incorrect) measurement
• Ignoring breast shape: Different breast shapes may require different bra styles even with the same size
• Not checking the fit: Always try on bras and adjust the straps and band for proper fit
• Assuming size stays constant: Your bra size can change with weight fluctuations, pregnancy, or aging

Understanding Sister Sizes

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

• 34C and 32D are sister sizes (both have the same cup volume)
• 36B and 34C are sister sizes
• 38A and 36B are sister sizes

Understanding sister sizes can be helpful when:

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

When to Get Professionally Fitted

While our calculator provides excellent results, consider getting professionally fitted if:

• You’re experiencing significant discomfort with your current bras
• You’ve had major weight changes (gain or loss)
• You’re pregnant or breastfeeding
• You’ve had breast surgery
• You’re buying expensive bras (worth getting the perfect fit)

Bra Size Statistics and Trends

According to a 2022 study by the National Institutes of Health, approximately 80% of women wear the wrong bra size. The most common issues include:

• Band size too large (34% of women)
• Cup size too small (28% of women)
• Both band and cup incorrect (18% of women)

The average bra size in the United States has changed significantly over the past few decades:

• 1990s: 34B
• 2000s: 36C
• 2010s: 36DD
• 2020s: 38DD

Research from Centers for Disease Control and Prevention shows that proper bra fitting can reduce back pain by up to 55% in women who previously wore ill-fitting bras.

International Bra Size Conversion

Bra sizes vary by country. Here’s a quick conversion guide:

US Size	UK Size	EU Size	France Size	Italy Size	Australia Size
32A	32A	70A	85A	1	8A
34B	34B	75B	90B	2	10B
36C	36C	80C	95C	3	12C
38D	38D	85D	100D	4	14D
40DD	40E	90E	105E	5	16E

Tips for Maintaining Bra Health

• Wash properly: Hand wash or use a delicate cycle with a lingerie bag
• Rotate bras: Don’t wear the same bra two days in a row to maintain elasticity
• Replace regularly: Bras should be replaced every 6-12 months depending on wear
• Store correctly: Keep bras in a drawer (not hanging by straps) to maintain shape
• Adjust straps: Straps should be snug but not digging in – they provide only 10% of support

Special Considerations

For Athletic Women

Women with a more muscular build may need to:

• Size up in the band if measurements fall between sizes
• Look for bras with wider bands for better support
• Consider racerback styles for better shoulder support

For Post-Surgical Patients

After breast surgery (augmentation, reduction, or mastectomy):

• Wait until cleared by your surgeon before measuring (typically 6-8 weeks)
• Look for post-surgical bras with soft, seamless fabric
• Consider front-closure bras for easier dressing
• Get professionally fitted as your size may change during healing

For Nursing Mothers

Breastfeeding women should:

• Measure frequently as size can change rapidly
• Look for nursing bras with easy-access clips
• Choose soft, breathable fabrics to prevent mastitis
• Consider sleep bras for overnight comfort and support

Frequently Asked Questions

Why do I get different sizes from different calculators?

Different calculators may use slightly different algorithms or rounding methods. Our calculator uses the most current industry standards from the ASTM International for bra sizing.

How often should I measure my bra size?

We recommend checking your size every 6 months, or whenever you notice:

• Your band rides up in the back
• Your straps dig into your shoulders
• Your cups wrinkle or gap
• You experience breast tissue spillage
• You’ve had significant weight changes

Can my bra size change throughout the month?

Yes, hormonal fluctuations during your menstrual cycle can cause temporary size changes. Many women experience:

• Up to 1 cup size increase in the week before menstruation
• Slight band size fluctuations due to water retention
• Increased sensitivity that may affect comfort

What’s the most common bra fitting mistake?

The most common mistake is wearing a band size that’s too large. Many women think a larger band is more comfortable, but it actually reduces support. The band should be snug enough that you can only fit one finger underneath when new.

Final Thoughts

Finding your perfect bra size is a journey that combines precise measurement with personal comfort preferences. Remember that:

• Your size may vary slightly between brands due to different manufacturing standards
• Comfort is just as important as the numbers – if it feels wrong, try a different size
• Different bra styles (sports, strapless, push-up) may fit differently even in the same size
• Your body changes over time – regular measurements ensure continued comfort

Use our calculator as a starting point, but always try on bras to confirm the fit. When in doubt, consult with a professional fitter at a reputable lingerie store.