Cup Size Chart
This cup size chart shows every standard cup size from AA to K with the exact measurement difference, approximate volume, and equivalents in US, UK, and EU sizing systems. Use it as a quick reference alongside our bra size calculator for the most accurate fit.
The inch difference between bust and underbust determines your cup size
Complete Cup Size Reference
A cup size chart is a standardized reference that maps each cup letter to the inch difference between bust and underbust measurements, covering sizes from AA (less than 1 inch) through K (11 inches) across the three major international sizing systems. The US system uses letter doubling after D -- DD, DDD -- while the UK system uses sequential single and double letters (DD, E, F, FF, G, GG). The European system follows a simpler A through K sequence with no doubled letters. Despite these naming differences, the physical cup volume at each step remains equivalent across systems when the band size matches. According to market research compiled by Bratabase and industry data, the average US bra size has shifted from 34B in 1991 to 34DD, reflecting improved sizing awareness and expanded retail ranges rather than population-wide body changes alone. The volumes listed below are calibrated to a 34 band, the most commonly purchased band size in the United States. For volumes at other band sizes, see the band-adjusted volume table further down this page.
| Cup | Difference (in) | Difference (cm) | US Name | UK Name | EU Name | Volume (34 band) |
|---|---|---|---|---|---|---|
| AA | <1" | <2.5 cm | AA | AA | AA | ~65 ml |
| A | 1" | 2.5 cm | A | A | A | ~130 ml |
| B | 2" | 5 cm | B | B | B | ~200 ml |
| C | 3" | 7.5 cm | C | C | C | ~275 ml |
| D | 4" | 10 cm | D | D | D | ~360 ml |
| DD | 5" | 12.5 cm | DD | DD | E | ~450 ml |
| DDD / F | 6" | 15 cm | DDD (F) | E | F | ~550 ml |
| G | 7" | 17.5 cm | G | F | G | ~660 ml |
| H | 8" | 20 cm | H | FF | H | ~780 ml |
| I | 9" | 22.5 cm | I | G | I | ~900 ml |
| J | 10" | 25 cm | J | GG | J | ~1030 ml |
| K | 11" | 27.5 cm | K | H | K | ~1170 ml |
Visual cup size comparison at the same band size. Each letter represents one additional inch of difference.
How Cup Volume Changes with Band Size
Cup volume is not fixed by the letter alone -- it scales proportionally with band circumference, which is why a 32D and a 38D hold different amounts of breast tissue despite sharing the same cup letter. Bra manufacturers design cup molds that increase in volume as the band size rises, adding approximately 35 to 50 ml per band increment depending on the cup letter. A C cup at band 30 holds roughly 240 ml, while the same C cup at band 40 holds approximately 380 ml -- a difference of nearly 60%. This scaling relationship is the foundation of the sister sizing concept, where 34C, 32D, and 36B all hold approximately the same 275 ml of cup volume because the band and cup adjustments offset each other. Our breast size chart illustrates this relationship with body-type context. The table below shows approximate cup volumes in milliliters across common band sizes for the five most purchased cup letters.
| Band | A Cup | B Cup | C Cup | D Cup | DD Cup |
|---|---|---|---|---|---|
| 30 | ~100 ml | ~160 ml | ~230 ml | ~310 ml | ~400 ml |
| 32 | ~115 ml | ~180 ml | ~250 ml | ~340 ml | ~430 ml |
| 34 | ~130 ml | ~200 ml | ~275 ml | ~360 ml | ~450 ml |
| 36 | ~150 ml | ~220 ml | ~300 ml | ~390 ml | ~480 ml |
| 38 | ~170 ml | ~245 ml | ~330 ml | ~420 ml | ~520 ml |
| 40 | ~190 ml | ~270 ml | ~360 ml | ~460 ml | ~560 ml |
How to Read This Cup Size Chart
Reading a cup size chart requires two body measurements and one subtraction. The bust measurement is taken at the fullest point of the chest with a soft tape held level, and the underbust measurement is taken snugly around the ribcage directly below the breasts, following the ASTM D6240 standard. Subtracting the underbust from the bust produces the cup difference in inches -- each inch maps to one cup letter starting at A for 1 inch. In the chart above, find your difference in the first column and read across for the corresponding cup letter in US, UK, and EU naming conventions. The volume column provides approximate cup capacity calibrated to a 34 band. If your band size differs from 34, the volume-by-band table earlier on this page shows how cup capacity shifts with band circumference. For example, a bust measurement of 37 inches minus an underbust of 33 inches yields a 4-inch difference, which corresponds to a D cup. The 33-inch underbust rounds to band 34, making the full size 34D with an approximate volume of 360 ml at that band.
Common Cup Size Misconceptions
Cup size misconceptions are widespread and contribute directly to the estimated 80% of women wearing incorrectly sized bras, according to fitting industry data cited across multiple professional sources. The most persistent myth is that a D cup is objectively large, when the cup size chart above shows it represents just a 4-inch measurement difference -- a modest proportion on smaller band sizes. A second common error is treating cup letters as fixed volumes, when a D cup at band 30 holds approximately 295 ml while the same letter at band 40 holds roughly 460 ml. The notion that DD is "double D" or twice the size of D is linguistically misleading -- DD is simply one inch more than D, the same single-inch increment as any other adjacent cup. These misunderstandings cause many women to avoid accurate sizing, defaulting to sizes they associate with perceived social norms rather than their actual measurements. The four most impactful misconceptions, based on fitting professional feedback, are addressed below with reference to the data in this cup size chart.
A D cup is not "big"
D represents just 4 inches of difference between bust and underbust. It is one of the most commonly worn sizes in the US. On a smaller band like a 30, a D cup looks quite modest. The perception of D as large comes from outdated sizing that pushed most women into A-D when the full range extends well beyond.
Cup size is not fixed
A D cup on a 32 band is physically smaller than a D cup on a 38 band. The letter only describes the proportional difference, not an absolute volume. Two people can both wear a D cup and have noticeably different breast sizes if their band sizes differ.
DD is not double D
DD is just one inch more than D, not twice the size. The jump from D to DD is the same single-inch increment as B to C or C to D. The name "double D" is misleading and contributes to the misconception that DD is dramatically larger than D.
There are sizes beyond DDD
US sizing goes to K and beyond. UK sizing extends even further with KK, L, and LL. Specialty brands like Elomi, Panache, and Goddess routinely manufacture sizes up to UK K cup. If you have been wearing a DDD because it was the largest in store, there may be a better-fitting size waiting.
Use this cup size chart alongside our calculator for the most accurate fit. For a breakdown of how each size actually looks and feels, see our cup size comparison. Since breast shape also affects how a cup fits, our breast shape guide matches nine shape types to recommended bra styles. Teens starting their sizing journey will find our teen bra size guide helpful for age-appropriate starter recommendations. If you are active, the sports bra size calculator adjusts for the compression and encapsulation fit that exercise bras require.
Frequently Asked Questions
What is the biggest cup size?
In standard US sizing, K is the largest commonly manufactured cup size, representing an 11-inch difference between bust and underbust measurements. UK sizing extends further with KK, L, and LL offered by specialty brands like Elomi and Goddess. Custom orders from bespoke manufacturers can accommodate even larger sizes beyond the standard chart range.
Is a cup size the same on every band?
Cup size is not the same on every band because cup volume scales proportionally with band circumference. A 30D holds approximately 310 ml while a 40D holds roughly 460 ml, even though both carry the same letter. This scaling is why sister sizing works -- adjusting the band up or down while changing the cup letter in the opposite direction maintains nearly identical cup volume.
What cup size is most common?
The most commonly purchased bra size in the United States is 34DD, according to retail sales data from major lingerie retailers. However, professional fitting experts estimate that approximately 80 percent of women wear an incorrect bra size, which means the true average cup size may differ from purchasing trends when measured accurately.