What is the ABTF method?

The ABTF method uses your actual underbust measurement as the band size, rather than adding inches. The band is responsible for most of a bra's support, so a correct band measurement is essential for a good fit.

Do you store my measurement data?

No. All calculations happen instantly in your browser. We do not store, sell, or share your body measurements. Your privacy is our priority.

Find Your Perfect Bra & Breast Size with BestBraSizeCalculator.com

Use our bra and breast size calculator for precise measurements, fit tips, and international conversions for every body.

Measure your size at home

Bra Size Calculator

Advanced Mode (ABTF-style)

Use snug/tight underbust and standing/leaning/lying bust to get a recommended try-on range and style tips.

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Measurement Unit:

Band Size (cm)

Bust Size (cm)

Measurement Guide

Band Size

Measure around your ribcage, just below your breasts. The tape should be snug but not tight.

Bust Size

Measure around the fullest part of your breasts, keeping the tape measure parallel to the floor.

The Science Behind Our Calculation

Understanding how we calculate your perfect bra size

Band Size Calculation

Your snug underbust measurement becomes your band size. The band provides 80% of a bra's support, so it must fit firmly and stay parallel to the ground. We use the direct underbust method, not the outdated +4 inch approach.

Cup Size Calculation

Cup size is determined by the difference between your bust measurement and your band size. Each inch of difference represents one cup size increment (1"=A, 2"=B, 3"=C, etc.).

Expert Note

Remember: A calculator is a starting point, not a verdict. Shape matters just as much as size. Whether you are 'shallow' or 'projected', 'full on top' or 'full on bottom' can affect how a bra fits. We recommend using our result as a baseline and trying on bras to see what works best for your unique body shape.

Learn more about our methodology

Brand Size Converter

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Your Size

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Size Guide

Enter your current bra size and select the brands you want to convert between. The converter will help you find your equivalent size in different brands.

Tips for Best Results:

Enter your size exactly as it appears on your current bra
Make sure to select both the source and target brands
Different brands may have slightly different sizing standards
Always try on bras when possible for the best fit

Sister Bra Sizes

If your band feels tight/loose or your size is out of stock, sister sizes help keep similar cup volume while adjusting support.

Find Sister Sizes

Bra Size Chart in CM & Inches

Use our comprehensive size chart to find your perfect fit. Compare measurements in both centimeters and inches.

Bra Size Chart in CM & Inches

Size	In cm		In Inches
	Underbust	Overbust	Underbust	Overbust
28A	66 - 76	72 - 75	26.0 - 30.0	28.5 - 29.5
28B	66 - 76	75 - 77	26.0 - 30.0	29.5 - 30.5
28C	66 - 76	77 - 80	26.0 - 30.0	30.5 - 31.5
28D	66 - 76	80 - 83	26.0 - 30.0	31.5 - 32.5
28DD	66 - 76	83 - 85	26.0 - 30.0	32.5 - 33.5
28E	66 - 76	85 - 88	26.0 - 30.0	33.5 - 34.5
28F	66 - 76	88 - 90	26.0 - 30.0	34.5 - 35.5
28G	66 - 76	90 - 93	26.0 - 30.0	35.5 - 36.5
30A	71 - 81	77 - 80	28.0 - 32.0	30.5 - 31.5
30B	71 - 81	80 - 83	28.0 - 32.0	31.5 - 32.5

International Bra Size Conversion

Convert your bra size across different international sizing systems. Find your perfect fit worldwide.

Global Size Conversion

US/UK	UK	EU	FR	IT	JP	AU/NZ	DE
28AA	28AA	70AA	85AA	3AA	70AA	6AA	70AA
28A	28A	70A	85A	3A	70A	6A	70A
28B	28B	70B	85B	3B	70B	6B	70B
28C	28C	70C	85C	3C	70C	6C	70C
28D	28D	70D	85D	3D	70D	6D	70D
28DD	28DD	70E	85E	3E	70E	6DD	70E
28DDD	28E	70F	85F	3F	70F	6E	70F
28G	28F	70G	85G	3G	70G	6F	70G
28H	28FF	70H	85H	3H	70H	6FF	70H
28I	28G	70I	85I	3I	70I	6G	70I

Launch the CM converter

How It Works: 3 Steps to Your Best Fit

Don't just guess your bra size. Follow our evidence-based workflow used by the ABTF community.

1. Measure Yourself

Learn how to take 6 accurate measurements at home using a soft tape measure. Our illustrated guide shows exactly where to place the tape.

Read Measurement Guide

2. Calculate Your Size

Enter your measurements into our ABTF calculator to get a starting size range in US, UK, EU, JP, and AU systems.

Use Calculator

3. Verify the Fit

Try on bras in your calculated size range and run our fit check. Learn the signs of a well-fitting bra vs common fit problems.

Check Fit Signs

Tools & Resources

Sister Sizes Size Chart Fit Guide Blog

Complete Bra Size Guide

Explore our comprehensive guide to find detailed information about your specific bra size

Small Band Sizes

Perfect for petite frames (28-32)

View Sizes→

Medium Band Sizes

Most common sizes (34-40)

View Sizes→

Large & Extended

Fuller figures (42-52)

View Sizes→

View Complete Size Guide

Expert Bra Measurement Blog

Discover professional tips, guides, and the latest insights about bra fitting and measurement.

How to Measure Your Bust

Learn the professional way to measure your bust size accurately.

How to Measure Your Waist

Discover the correct way to measure your waist for perfect bra fitting.

Bra Size Calculator Guide

Learn how to use our calculator effectively for accurate measurements.

Find Your Size by Country

Get localized sizing information, popular brands, and shopping tips for your country

AustraliaAU BrazilUS CanadaUS FranceFR GermanyDE IndiaUS SingaporeUS South KoreaUS United KingdomUK United StatesUS

Each page includes local sizing standards, popular brands, and where to shop

Built on Community-Validated Methods

👩‍💼

ABTF

Method Used

🏷️

100+

Brands Calibrated

📚

50+

Expert Guides

🌍

Languages

Frequently Asked Questions

How accurate is the bra size calculator?

Our calculator uses professional measurement techniques and algorithms to provide highly accurate results. However, for the best fit, we recommend:

Taking measurements at least twice to ensure accuracy
Measuring without a padded bra
Following the measurement guide carefully
Considering professional fitting for the most precise results

How often should I measure my bra size?

It's recommended to measure your bra size every 6 months or when you experience significant changes such as:

Weight gain or loss
Pregnancy or nursing
Hormonal changes
After significant exercise routine changes

What's the difference between US and UK bra sizes?

The main differences between US and UK bra sizes are:

UK sizes use double letters (DD, FF, GG) while US sizes use single letters
Band sizes are measured in inches in both systems
Some cup sizes may have different names in each system
Our calculator automatically converts between these systems

How do I know if my bra fits correctly?

A well-fitting bra should have these characteristics:

The band should be snug but comfortable
Straps should not dig into shoulders
Cups should fully contain breast tissue
No spillage or gaping in cups
Center gore should lie flat against chest

What should I do if my size is between two measurements?

When your measurements fall between sizes, consider these factors:

Try both sizes to determine the best fit
Consider the style and brand of the bra
Check if the bra has adjustable features
Look for sister sizes that might work better

How do I care for my bras to maintain their fit?

Proper bra care is essential for maintaining fit and longevity:

Hand wash or use delicate cycle with cold water
Use mild detergent specifically for delicates
Air dry flat to maintain shape
Rotate between multiple bras
Replace bras every 6-12 months

Why Women Trust Our Calculator

Built on modern fitting methods and real-world feedback

Modern ABTF Method

We use the A Bra That Fits measurement approach — no outdated +4 inch rule. Your band size equals your actual underbust measurement for better support.

7 International Systems

US, UK, EU, FR, IT, JP, AU — all in one place. Shop confidently from any brand, anywhere in the world, without guessing conversions.

Free & No Sign-Up

No email required, no account needed. All calculations happen in your browser. Your measurements are never stored or shared.

Medically Reviewed Content

Our guides on bra fit, breast health, and body changes are reviewed by healthcare professionals. Trustworthy information you can rely on.

Specialized Calculators

Dedicated tools for sports bras, nursing, pregnancy, and more. One-size-fits-all doesn't work for bras — neither should your calculator.

100+ Brand Calibrations

Every brand fits differently. Our brand-specific offsets help you find the right size in Victoria's Secret, ThirdLove, and 100+ other brands.

Why Accurate Measurements Matter

✓Proper support and comfort throughout the day
✓Better posture and reduced back pain
✓Enhanced confidence and appearance
✓Longer-lasting bras with proper care

Expert Fitting Tips

•Measure yourself every 6-12 months
•Wear a non-padded bra when measuring
•Stand straight with arms at your sides
•Take measurements in the morning

Important: Your Starting Size, Not Your Final Size

Our calculator provides a starting size range based on body measurements. Bra fit varies by brand, style, breast shape, and personal comfort — factors no calculator can fully account for. Always try on bras to confirm fit, and use our fit check guide to verify support, comfort, and cup coverage.

Privacy First

Your measurements are calculated in your browser. We do not store your body data.

Expert Reviewed Content

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