Bra Size Calculator: Find Your Exact Size in 60 Seconds
Enter your 6 measurements below. Our calculator uses the most accurate method to determine your true bra size across US, UK, and EU sizing systems.
Bra Size Calculator
How the Calculator Works
Our 6-measurement method captures your true shape, not just two numbers. Here is how it works.
Measure Your Underbust
Take three underbust measurements at different tensions: loose (relaxed), snug (comfortably fitted), and tight (exhaled and pulled).
Measure Your Bust
Take three bust measurements in different positions: standing upright, leaning 90 degrees forward, and lying flat on your back.
Get Your True Size
We average your measurements and calculate your band, cup, and sister sizes across US, UK, and EU sizing systems instantly.
Understanding Your Results
What each part of your bra size means and why sister sizes matter.
Band Size (The Number)
Your band size comes from the snug underbust measurement, rounded to the nearest even number. The band provides 80% of a bra’s support. A properly fitted band sits level around your torso and stays in place without riding up.
Cup Size (The Letter)
Cup size is the difference between your average bust measurement and your band size. Each inch of difference equals one cup size. A cup is not a fixed volume. A 32D cup is smaller than a 38D cup because cup volume scales with band size.
Sister Sizes
Sister sizes share the same cup volume with a different band fit. For example, 32D, 34C, and 36B all hold the same cup volume. Try a sister size when your calculated size feels too tight or too loose in the band.
International Equivalents
Your results show US, UK, and EU sizes simultaneously. US and UK share band numbers but differ in cup letter progression after D. EU uses centimeter-based bands (70, 75, 80) and its own cup letters.
Quick Measurement Guide
How to take all 6 measurements at home with just a soft measuring tape.
Underbust: Loose, Snug, Tight
Wrap the tape directly under your bust where the band sits. Measure three times: relaxed (tape not pulled), snug (fitted without compressing), and tight (exhale completely and pull the tape as tight as it goes).
Bust: Standing, Leaning, Lying
Measure at the fullest point of your bust. Standing upright gives one reading. Leaning forward at 90 degrees lets tissue fall naturally. Lying flat on your back gives the third. All three positions capture how tissue distributes differently.
Bra Size Chart Quick Reference
Common band and cup size combinations with their measurements.
| Band Size | Underbust Range | A Cup Bust | B Cup Bust | C Cup Bust | D Cup Bust | DD Cup Bust |
|---|---|---|---|---|---|---|
| 30 | 28″-30″ | 31″ | 32″ | 33″ | 34″ | 35″ |
| 32 | 30″-32″ | 33″ | 34″ | 35″ | 36″ | 37″ |
| 34 | 32″-34″ | 35″ | 36″ | 37″ | 38″ | 39″ |
| 36 | 34″-36″ | 37″ | 38″ | 39″ | 40″ | 41″ |
| 38 | 36″-38″ | 39″ | 40″ | 41″ | 42″ | 43″ |
| 40 | 38″-40″ | 41″ | 42″ | 43″ | 44″ | 45″ |
International Size Conversion
How bra sizes translate between US, UK, EU, Australian, and Japanese sizing systems.
Band Size Conversion
US/UK bands use inches (30, 32, 34, 36). EU bands use centimeters (65, 70, 75, 80). A US 32 equals an EU 70. Australian sizing follows UK bands. Japanese bands use centimeters but with different increments than EU.
Cup Size Conversion
US cups after D go DD, DDD/F, G, H. UK cups after D go DD, E, F, FF, G, GG, H. EU cups follow a simpler single-letter progression: A, B, C, D, E, F, G. A US DDD is a UK E and an EU F.
| US Band | UK Band | EU Band | AU Band |
|---|---|---|---|
| 30 | 30 | 65 | 8 |
| 32 | 32 | 70 | 10 |
| 34 | 34 | 75 | 12 |
| 36 | 36 | 80 | 14 |
| 38 | 38 | 85 | 16 |
| 40 | 40 | 90 | 18 |
Common Sizing Issues
Signs your current bra does not fit correctly and what adjustments to make.
Band Rides Up in Back
Band is too large. Try a smaller band with the next cup size up.
Cups Overflow or Spill
Cup is too small. Move up one or two cup sizes while keeping the same band.
Straps Dig Into Shoulders
Band is not supporting enough. A tighter band relieves pressure on straps.
Gaps or Wrinkles in Cups
Cup is too large. Move down one cup size or try a different cup shape.
The Most Accurate Online Bra Size Calculator
Finding the right bra size is more than picking a number and a letter. Studies show that up to 80% of women wear the wrong bra size, leading to discomfort, poor support, and even back pain. The problem is not the women. It is the outdated two-measurement method most stores and online calculators still use.
Our bra size calculator uses 6 measurements instead of 2. Three underbust measurements at different tensions (loose, snug, tight) capture your true band size. Three bust measurements in different positions (standing, leaning forward at 90 degrees, lying down) account for how breast tissue distributes across postures. This gives a dramatically more accurate result than any single-position measurement.
How Bra Sizing Works
A bra size has two components: the band size (the number) and the cup size (the letter). The band size comes from your snug underbust measurement, rounded to the nearest even number. The cup size comes from the difference between your average bust measurement and your band size. Each inch of difference corresponds to one cup size: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D, 5 inches = DD/E, and so on.
What most people do not realize is that cup size is relative to band size. A 32D and a 36D do not have the same cup volume. The 36D has a larger cup. This is why sister sizes matter. A 32D, 34C, and 36B all share the same cup volume, just with different band fits. Our calculator shows your sister sizes automatically so you have options when shopping.
US, UK, and EU Size Differences
Bra sizing systems vary by country. US sizes use even numbers for bands and letter progression (A, B, C, D, DD, DDD/F, G, H). UK sizes follow a different cup progression after D (DD, E, F, FF, G, GG, H). EU sizes use centimeter-based bands (65, 70, 75, 80…) and letter cups. Our calculator converts across all three systems so you can shop any brand worldwide with confidence. See the full breakdown on our bra size chart.
Frequently Asked Questions
Common questions about bra sizing, measuring, and fit.
Ready to Find Your True Bra Size?
Take 2 minutes to measure yourself and discover the difference a properly fitting bra makes.
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