Cup Size Visuals
Cup letters are confusing because a letter is not a size on its own — it is a difference between two measurements, and the volume it stands for changes with the band. A 32D and a 40D share a letter but hold very different amounts of tissue, which is why photos and comparisons that show a cup letter without a band are misleading. This page shows what each cup from AA to K means in plain terms: the bust-to-band difference behind the letter, the matching letters in US, UK and EU sizing, the approximate volume at a 34 band, and a simple visual comparison so you can see how the steps grow. Everything here is approximate and illustrative — real cups vary by brand, style and shape — but the pattern is real: each cup step adds volume, and each step adds more than the one before it.
If you do not know your own size yet, start with the bra size calculator or the measuring guide. If you already have a size and want to see how it converts, the bra size chart has the full conversion tables, and the sister size calculator shows the sizes that hold a similar cup volume on a different band.
Cup Sizes Compared: AA to K
The table below uses US cup letters. The bust-minus-band difference is the same idea in every system — each inch of difference is one cup step — but the letters diverge above DD: the US goes DD, DDD, G, H, while the UK goes DD, E, F, FF, G, and the EU goes E, F, G, H. Volumes are approximate figures for a 34 band, published by Cup Size Guide, and they rise with the band: a D cup on a 32 band holds roughly 325 ml, while the same letter on a 38 band holds roughly 430 ml.
| US cup | Bust − band difference | US | UK | EU | Approx. volume at 34 band |
|---|---|---|---|---|---|
| AA | Under 1 in | AA | AA | AA | ~65 ml |
| A | 1 in | A | A | A | ~130 ml |
| B | 2 in | B | B | B | ~200 ml |
| C | 3 in | C | C | C | ~275 ml |
| D | 4 in | D | D | D | ~360 ml |
| DD | 5 in | DD | DD | E | ~450 ml |
| DDD | 6 in | DDD | E | F | ~550 ml |
| G | 7 in | G | G | G | ~660 ml |
| H | 8 in | H | H | H | ~780 ml |
| I | 9 in | I | I | I | larger still — varies widely by brand |
| J | 10 in | J | J | J | larger still — varies widely by brand |
| K | 11 in | K | K | K | larger still — varies widely by brand |
Volumes are approximate and vary by brand, style and breast shape. Cups above H are listed without a volume figure because published estimates for them disagree widely — the pattern (each step adds more than the last) still holds. Source for AA–H volumes at a 34 band: Cup Size Guide, cup-size comparison.
Seeing the Steps Grow
The bars below show the same approximate volumes at a 34 band, so you can see at a glance how the steps grow. These bars are illustrative, not to scale — they are a visual aid for comparing cup letters, not a measurement of any real breast. The key thing to notice is the spacing: the jump from A to B is smaller than the jump from G to H, because each cup step adds a larger volume than the one before it.
Illustrative bars, not to scale. Approximate volume per cup at a 34 band; volume rises with band size.
What Changes From Cup to Cup
Three things change as you move up the cup letters, and they change together. First, the volume grows — and it grows faster with each step, which is why the difference between a B and a C feels smaller than the difference between a G and an H. Second, the cup gets deeper and wider: a larger cup is not just a smaller cup scaled up, it is a differently shaped piece of fabric with more projection and a wider wire. Third, the support the cup needs grows with it, which is why larger cups tend to come with wider straps, stronger bands and more structured cups — the band and the straps have more weight to carry.
What does not change is the meaning of the letter: one cup step is always one inch of bust-to-band difference in the system you are using. That is the whole system. If your bust measures 4 inches more than your band, you are a D cup in US sizing; if it measures 5 inches more, you are a DD. The confusion starts when the letter is read without the band, because the same 4-inch difference holds far more volume on a 40 band than on a 30 band.
The Same Letter on a Different Band
This is the single most misunderstood idea in bra sizing, so it is worth saying plainly: a cup letter has no fixed volume. A 30D, a 34D and a 40D all describe a 4-inch difference, but the cups hold different amounts of tissue because the band they sit on is a different size around. That is why sister sizes work — a 34C and a 32D hold roughly the same cup volume, because the smaller band is paired with a larger cup letter to keep the volume steady.
It also explains why two people who both wear a D cup can look completely different, and why neither of them is wearing the wrong size. The letter is only half a size. Always read it with the band number in front of it, and always convert both parts together when you switch systems — the global size converter does exactly that.
Cup Size Is Not Breast Shape
Volume is only half the story. Two people with the same band and cup can need different bras because their tissue is distributed differently — fuller on top, fuller on the bottom, shallow, or close-set. A cup that fits one shape can gap or spill on another at exactly the same size. If your measured size fits in some styles and not others, the breast shape guide and the fit problem solver are the next steps, not a different size.
Keep Exploring
- Bra size chart — US, UK, and EU band and cup sizes in one conversion table.
- Bra size calculator — find your estimated size from your measurements.
- Sister size calculator — sizes with a similar cup volume on a different band.
- Breast volume calculator — estimate cup volume in ml for your band and cup.
- How to measure your bra size — the measuring guide behind every number on this page.
Frequently Asked Questions
Is a D cup big?
It depends entirely on the band. A 30D holds far less volume than a 40D, because cup volume grows with the band. A D cup means a 4-inch difference between bust and band — on a smaller band that is a modest cup, and on a larger band it is a much fuller one. The letter alone never tells you how large a cup is.
Why does the same cup letter look different on different people?
Because a cup letter is a difference, not a fixed volume. It measures how far the bust sits beyond the band, so the same letter on a 32 band and a 38 band holds different amounts of tissue. Shape matters too: the same volume can look fuller or shallower depending on projection and root width.
What actually changes from one cup to the next?
Volume — and each step adds more than the one before it. At a 34 band, moving from A to B adds roughly 70 ml per cup, while moving from G to H adds roughly 120 ml. The cup also gets deeper and wider, which is why a larger cup needs a stronger band and wider straps to stay comfortable.
What should I do if I fall between two cup sizes?
Try both, and try a sister size as well. If the smaller cup spills and the larger cup gaps, the issue is often the style rather than the size — a different cut in the same size can fit where another cut fails. If both cups feel wrong in the same way, re-check your measurements first.