Bust to Bra Size Converter – Quick & Accurate

Bust to Bra Size Converter

Accurate bra size calculations for multiple sizing systems

Your Bra Sizes

International Bra Size Conversion

US UK EU France/Spain Australia/NZ
32A 32A 70A 85A 10A
32B 32B 70B 85B 10B
32C 32C 70C 85C 10C
32D 32D 70D 85D 10D
34A 34A 75A 90A 12A
34B 34B 75B 90B 12B
34C 34C 75C 90C 12C
34D 34D 75D 90D 12D
34DD 34DD 75E 90E 12DD
36A 36A 80A 95A 14A
36B 36B 80B 95B 14B
36C 36C 80C 95C 14C
36D 36D 80D 95D 14D
36DD 36DD 80E 95E 14DD
38A 38A 85A 100A 16A
38B 38B 85B 100B 16B
38C 38C 85C 100C 16C
38D 38D 85D 100D 16D
40B 40B 90B 105B 18B
40C 40C 90C 105C 18C
40D 40D 90D 105D 18D

How to Measure & Calculate

Step 1: Measure Band Size

Wrap a measuring tape around your ribcage directly under your breasts. Keep the tape snug but not tight. Round to the nearest whole number.

Step 2: Measure Bust Size

Measure around the fullest part of your bust while wearing an unpadded bra. Keep the tape loose and parallel to the ground.

Step 3: Calculate Difference
Cup Size = Bust Measurement – Band Measurement

Each inch of difference corresponds to a cup size. For example, 1 inch = A cup, 2 inches = B cup, 3 inches = C cup, and so on.

Important Note: Different countries apply varying methods to calculate band sizes. US sizing typically adds 4-5 inches to the underbust measurement for even numbers, while UK sizing may use the measurement directly or add fewer inches.

Calculation Steps

  1. Measure your underbust circumference snugly around your ribcage, just below your breasts
  2. Measure your bust at the fullest point while wearing a non-padded bra
  3. Calculate the difference between bust and band measurements
  4. Match the difference to the cup size chart for your region
  5. Combine the band size with the cup size to get your complete bra size

Cup Size Reference Chart

Difference (Inches) Difference (CM) US Cup UK Cup EU Cup
<1 10-11 AA AA AA
1 12-13 A A A
2 14-15 B B B
3 16-17 C C C
4 18-19 D D D
5 20-21 DD/E DD E
6 22-23 DDD/F E F
7 24-25 G F G
8 26-27 H FF H
9 28-29 I G I
10 30-31 J GG J

Regional Sizing Differences

United States

US sizing typically adds 4-5 inches to the underbust measurement to determine band size. Cup sizes progress alphabetically with double letters (DD, DDD) for larger sizes.

United Kingdom

UK sizing uses the underbust measurement more directly, with minimal adjustment. Cup progression includes double letters (DD, FF, GG) but differs from US sizing after D cup.

European Union

EU band sizes are measured in centimeters and appear as numbers like 70, 75, 80. Cup sizes follow a single-letter progression without double letters.

France & Spain

French and Spanish sizing adds 15cm to the underbust measurement. A 70EU becomes 85FR. Cup sizes follow the same single-letter system as EU sizing.

Australia & New Zealand

Australian sizing uses dress sizes (8, 10, 12) for band sizes. The system closely mirrors UK cup sizing with similar letter progressions.

Sister Sizes Explained

Sister sizes are alternative bra sizes that have the same cup volume but different band and cup letter combinations. When you go up one band size, you go down one cup size, and vice versa.

Smaller Band Your Size Larger Band
30D 32C 34B
32D 34C 36B
32DD 34D 36C
34DD 36D 38C
34E 36DD 38D
36E 38DD 40D
36F 38E 40DD
When to Try Sister Sizes: If the cups fit perfectly but the band feels too tight or too loose, try a sister size. This maintains the same cup volume while adjusting band comfort.

Common Fit Problems & Solutions

Problem Cause Solution
Band rides up back Band too loose Try a smaller band size
Cups overflow Cup too small Go up one or more cup sizes
Gaps in cups Cup too large Try a smaller cup size
Straps dig in Band too loose or cups too small Tighten band or increase cup size
Center panel lifts Cup too small or wrong style Increase cup size or try different style
Underwire pokes Wrong size or shape Check size and try different brands
Band feels tight Band too small Try larger band with smaller cup

Frequently Asked Questions

How often should I measure my bra size?
Remeasure every 6-12 months or whenever you experience weight changes of 10+ pounds, pregnancy, hormonal changes, or notice fit issues with your current bras. Your breast size can fluctuate throughout your life.
Why do different brands fit differently?
Bra sizing lacks universal standardization. Each manufacturer uses slightly different patterns, materials, and measurements. A 34C from one brand may fit differently than a 34C from another. Always try before buying when possible.
Should I add inches to my underbust measurement?
Modern fitting methods often recommend using your actual underbust measurement as your band size, or adding only 0-2 inches. The old method of adding 4-5 inches can result in bands that are too loose for proper support.
What if my measurements fall between sizes?
If you measure between band sizes, try both options. For cups, round up if closer to the next size. Remember that sister sizes offer alternative combinations with the same cup volume.
How tight should a new bra band be?
A new bra should fit comfortably on the loosest hook. This allows you to tighten it as the elastic stretches over time. You should be able to fit two fingers under the band, but it should not slide around your torso.
Do I need different sizes for different bra styles?
Yes, different styles (push-up, balconette, sports bra) may require slight size adjustments. Sports bras often run smaller, while some push-up styles may need a larger cup to accommodate padding.

Measuring Tips for Accuracy

Right Time to Measure

Measure in the middle of your menstrual cycle when breasts are at their average size. Avoid measuring during periods when breasts may be swollen or tender.

Proper Bra for Measuring

Wear a non-padded, well-fitting bra when measuring bust size. Avoid push-up or heavily padded bras that distort your natural breast size.

Tape Placement

Keep the measuring tape parallel to the ground all the way around. Check in a mirror to ensure the tape hasn’t twisted or slipped up or down.

Breathing Normally

Take measurements while breathing normally. Don’t hold your breath or suck in. The band measurement should be taken after a normal exhale.

Get Help If Possible

Having someone else take your measurements often yields more accurate results than measuring yourself, especially for the bust measurement.

Multiple Measurements

Take each measurement 2-3 times and use the average. Small variations are normal, and averaging helps eliminate outliers.

References

  • American Cancer Society. (2023). “Breast Changes and Conditions.” www.cancer.org
  • International Journal of Fashion Design, Technology and Education. (2020). “Bra Sizing and Fit in Different International Markets.”
  • McGhee, D. E., & Steele, J. R. (2010). “Breast biomechanics: What do we really know?” Physiology, 25(6), 375-383.
  • White, J., & Scurr, J. (2012). “Evaluation of professional bra fitting criteria for bra selection and fitting in the UK.” Ergonomics, 55(6), 704-711.
  • Greenbaum, A. R., Heslop, T., Morris, J., & Dunn, K. W. (2003). “An investigation of the suitability of bra fit in women referred for reduction mammaplasty.” British Journal of Plastic Surgery, 56(3), 230-236.
  • Wood, K., Cameron, M., & Fitzgerald, K. (2008). “Breast size, bra fit and thoracic pain in young women.” Chiropractic & Osteopathy, 16(1), 1.
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