Breast Size Chart
This breast size chart is a complete reference of every cup size from AA through K -- with the bust-to-underbust difference, approximate volume, and what each size looks like in practice.
Cup Size by Difference
Cup size is determined by the inch difference between the bust measurement taken at the fullest point and the underbust measurement taken snugly around the ribcage, following the methodology defined in ASTM D6240. Each inch of difference corresponds to one cup letter: 1 inch equals an A cup, 2 inches a B cup, 3 inches a C cup, and so on through K at 11 inches. The approximate volumes listed in this breast size chart are calibrated to a 34 band, the most commonly sold band size in the United States. Volume scales with band size -- a D cup at band 30 holds approximately 295 ml, while a D cup at band 38 holds roughly 430 ml. According to Bratabase market data, the average US bra size is now 34DD, representing a 5-inch bust-to-underbust difference. The three major sizing systems -- US, UK, and EU -- use identical cup letters through D but diverge above that point, with the US system using DD, DDD, G and the UK system using DD, E, F, FF.
| US Cup | UK Cup | EU Cup | Difference (in) | Difference (cm) | Volume (34 band) |
|---|---|---|---|---|---|
| AA | AA | AA | <1" | <2.5 cm | ~65 ml |
| A | A | A | 1" | 2.5 cm | ~130 ml |
| B | B | B | 2" | 5 cm | ~200 ml |
| C | C | C | 3" | 7.5 cm | ~275 ml |
| D | D | D | 4" | 10 cm | ~360 ml |
| DD | DD | E | 5" | 12.5 cm | ~450 ml |
| DDD / F | E | F | 6" | 15 cm | ~550 ml |
| G | F | G | 7" | 17.5 cm | ~660 ml |
| H | FF | H | 8" | 20 cm | ~780 ml |
| I | G | I | 9" | 22.5 cm | ~910 ml |
| J | GG | J | 10" | 25 cm | ~1050 ml |
| K | H | K | 11" | 27.5 cm | ~1200 ml |
Band Size Reference
Band size is the numerical component of a bra size, derived from the snug underbust measurement rounded to the nearest even number in the US and UK systems. The band provides approximately 80% of a bra's structural support, making correct band sizing more important than cup sizing for overall comfort and fit longevity. US and UK systems express bands in inches (28 through 46 in standard retail), while the European EN 13402 standard uses centimeters (60 through 105), incrementing by 5 rather than 2. Australian sizing uses dress-size numbers (6 through 24), and French sizing adds 15 to the EU centimeter measurement. According to professional fitting data, the most common band sizing error is wearing a band two sizes too large, which shifts the support burden onto the shoulder straps and causes the back band to ride up. The table below maps each underbust measurement range to the corresponding band number across all four major regional systems used in this breast size chart.
| Underbust (in) | Underbust (cm) | US/UK Band | EU Band | AU Band | FR Band |
|---|---|---|---|---|---|
| 26-27" | 66-69 cm | 28 | 60 | 6 | 75 |
| 28-29" | 71-74 cm | 30 | 65 | 8 | 80 |
| 30-31" | 76-79 cm | 32 | 70 | 10 | 85 |
| 32-33" | 81-84 cm | 34 | 75 | 12 | 90 |
| 34-35" | 86-89 cm | 36 | 80 | 14 | 95 |
| 36-37" | 91-94 cm | 38 | 85 | 16 | 100 |
| 38-39" | 96-99 cm | 40 | 90 | 18 | 105 |
| 40-41" | 101-104 cm | 42 | 95 | 20 | 110 |
| 42-43" | 106-109 cm | 44 | 100 | 22 | 115 |
| 44-45" | 111-114 cm | 46 | 105 | 24 | 120 |
Reading This Chart
Reading a breast size chart requires two measurements and a simple subtraction. First, measure the underbust circumference snugly around the ribcage -- this determines the band number. Second, measure the bust at its fullest point while wearing a non-padded bra or no bra -- this provides the bust number. Subtract the underbust from the bust, and the resulting difference in inches maps directly to a cup letter using the cup table above. Combining the band number with the cup letter produces the full bra size: a 32-inch underbust with a 3-inch difference yields a 32C. For cross-system shopping, the band table converts that same measurement into EU 70, AU 10, and FR 85. According to a 2024 survey of 1,075 US women published by Bra Size Calculator USA, 35.72% of respondents require cup sizes beyond the standard A-through-D range, which means the extended cup reference in this breast size chart (through K) serves more than one-third of the population. Use this chart alongside our bra size calculator for instant automated results.
For a guided walkthrough, use our bra size calculator or follow the step-by-step measuring guide. To convert between international sizing systems, try the size converter.
When to Re-Measure
Breast size is not static, and the measurements that determine your position on this breast size chart can shift due to weight fluctuations, hormonal changes, pregnancy, breastfeeding, menopause, and aging. A weight change of 10 pounds or more is enough to alter both band and cup measurements, as breast tissue contains a significant proportion of fat that responds to overall body composition changes. Hormonal fluctuations during the menstrual cycle can cause cup size to vary by up to half a size between the follicular and luteal phases. Professionals recommend re-measuring at least once every 12 months, or after any major life event that affects body weight or hormonal balance. Taking fresh measurements ensures the breast size chart continues to point you to the correct bra size rather than a size that fit months or years ago.
Bookmark this breast size chart for quick reference when shopping. To find your exact cup size, try our free bra size calculator -- it takes less than a minute. Parents looking for teen-appropriate sizing guidance will find our teen bra size guide covers first-bra starter styles and body-positive measurement tips. Cup size alone does not determine bra fit -- our breast shape guide explains how nine common shape types affect which bra style works best for your body. For active wear, the sports bra vs regular bra comparison outlines the structural differences that affect sizing for exercise.