Breast Volume Calculator
This calculator gives a rough estimate, not a measurement. Cup volume varies with breast shape, root width and projection, so no formula based on band and cup alone can give an exact number for your body. What it can do is give you a sensible ballpark — useful if you are curious how cup sizes compare, if you are comparing sister sizes, or if you simply want a concrete sense of what a cup letter holds in milliliters. Treat the result as an approximate range, and never use it for a medical decision.
The estimate works from published approximate cup volumes at a 34 band, adjusted for your band: volume rises roughly 10% for each band step up at the same cup letter, and falls roughly 10% for each step down. The result is shown as a range of about plus or minus 15% around the central estimate, because shape alone can move real volume by at least that much. Enter your band and cup below — US letters are used, and the global size converter can convert your size first if you shop in another system.
Estimate Your Cup Volume
Rough estimate: figures are approximate volumes per breast at a 34 band, adjusted about 10% per band step, and shown as a range of roughly ±15%. Real volume varies with shape, root width and projection. This tool is a fitting guide only — not a medical measuring tool.
Approximate Volume by Cup (34 Band)
The table below is the basis of the estimate: approximate volume per breast at a 34 band, as published by Cup Size Guide. Larger cups are not listed because published estimates for cups above H disagree too widely to quote responsibly — the pattern still holds (each step adds more than the last), but the numbers themselves are not settled enough to print.
| US cup | Approx. volume per breast at a 34 band |
|---|---|
| AA | ~65 ml |
| A | ~130 ml |
| B | ~200 ml |
| C | ~275 ml |
| D | ~360 ml |
| DD | ~450 ml |
| DDD | ~550 ml |
| G | ~660 ml |
| H | ~780 ml |
Source: Cup Size Guide, cup-size comparison (approximate volumes at a 34 band; a D cup at band 32 holds roughly 325 ml and at band 38 roughly 430 ml). Volumes are approximate and vary by brand, style and breast shape.
How the Estimate Is Calculated
Three steps, all visible. First, the calculator takes the published approximate volume for your cup at a 34 band from the table above. Second, it adjusts for your band: each band step above 34 multiplies the volume by about 1.10, and each step below 34 divides by about 1.10 — a rule that matches the published examples (a 32D at roughly 325 ml and a 38D at roughly 430 ml, against 360 ml at a 34 band). Third, it widens the result into a range of roughly plus or minus 15% and reports that range, not a single number, because shape alone can move real volume by that much. If your cup is above H, the calculator does not give a figure: published estimates there disagree too widely to be useful.
Why Volume Is Only Half the Story
The same volume can sit very differently on different bodies. A shallow shape spreads volume wider with less projection; a projected shape concentrates it forward. A wide root and a narrow root can hold the same volume in cups that look nothing alike. That is why two people with the same band, cup and volume estimate can need different bra styles — and why this calculator is a curiosity and comparison tool, not a fitting verdict. For fit, your measurements and the bra size calculator matter far more than any volume figure. To see how cup letters compare visually, try the cup size visuals page.
Keep Exploring
- Cup size visuals — what each cup from AA to K looks like compared.
- 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.
Frequently Asked Questions
How accurate is this breast volume estimate?
It is a rough estimate, not a measurement. The figures come from published approximate cup volumes at a 34 band, adjusted by about 10% per band step, and the result is shown as a range of roughly plus or minus 15%. Shape, root width and projection change real volume a lot — two people with the same band and cup can have quite different volumes.
Is the volume for one breast or both?
One breast — the volume of a single cup. If you want the combined volume of both breasts, double the figure. Cup volumes are always quoted per breast, because each cup holds one breast.
Can I use this volume to choose an implant size?
No. This calculator is a fitting guide for bras, not a medical tool. Implant sizing depends on chest width, tissue, skin and surgical planning, and only a qualified clinician can advise on it. Never use a bra-fitting estimate for a medical decision.
Why does the volume change when the band changes?
Because a cup letter is a difference, not a fixed volume. The same letter on a larger band sits on a larger ribcage, so the cup is wider and deeper and holds more. As a rough rule the volume rises about 10% for each band step up at the same cup letter — which is also why sister sizes work.