How this cup size comparison works
This is a visual cup size comparison—not a store fitting appointment. You set band and cup (or estimate from underbust and full bust), choose body shapes, and see two figures side by side. Estimated cup volume drives breast size on the model; body shape scales the frame separately so you can isolate “same letter, different look.”
- Pick a focus: same body with different cups, same size on different bodies, or free setup.
- Adjust band, cup, shape (shallower or more forward), and body type on each side.
- Use front, three-quarter, or side views—and zoom to the chest—to read outline differences.
- Copy the link or download an image when you want to save or share a comparison.
Why the same cup letter looks different on different bodies
Cup letters describe volume relative to band size—not a fixed look. A 34C on a petite frame sits differently on the torso than the same letters on a plus frame. Keep the size the same and change body shape to see that gap.
Cup volume chart (same band)
Illustrative one-side volume for a 34" band in the US letter sequence used by this tool. Real brands grade differently—use the numbers to see how letters step up, not as a fitting guarantee.
| Size | Cup | Est. volume (cc) |
|---|---|---|
| 34AA | AA | 225 |
| 34A | A | 280 |
| 34B | B | 335 |
| 34C | C | 390 |
| 34D | D | 445 |
| 34DD | DD | 500 |
| 34DDD | DDD | 555 |
| 34G | G | 610 |
| 34H | H | 665 |
Volume rises with each cup step on the same band. A letter on a larger band holds more tissue than the same letter on a smaller band—see sister sizes below.
Sister size chart
Sister sizes keep similar estimated cup volume while the band changes: up one band and down one cup (or the reverse). The preview flags pairs that match this relationship.
| Est. volume (cc) | Sister sizes (US) |
|---|---|
| ≈ 280 | 32B · 34A · 36AA |
| ≈ 335 | 32C · 34B · 36A |
| ≈ 390 | 32D · 34C · 36B · 38A |
| ≈ 445 | 32DD · 34D · 36C · 38B |
| ≈ 500 | 34DD · 36D · 38C · 40B |
Sister sizes help when a band feels too tight or loose but cup volume still feels right. They are not a promise every brand will fit the same.
US, UK, and EU cup letters
Letter sequences diverge after D. Switch the size chart in the tool to match the labeling you use; the comparison engine still steps volume by cup index.
| Step | US | UK | EU |
|---|---|---|---|
| 1 | AA | AA | AA |
| 2 | A | A | A |
| 3 | B | B | B |
| 4 | C | C | C |
| 5 | D | D | D |
| 6 | DD | DD | E |
| 7 | DDD | E | F |
| 8 | G | F | G |
| 9 | H | FF | H |
How to measure for a size estimate
Use a soft tape. Stand upright and breathe normally. Soft tissue compresses easily—keep the tape snug, not tight.
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- breastCup.measureStep2
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What this tool shows—and what it does not
Useful for
- Seeing why the same cup letter can look different on petite vs plus frames.
- Comparing two sizes or sister sizes before you shop or discuss fit.
- Turning underbust and full-bust numbers into a starting size estimate.
Not a substitute for
- A brand’s own size chart or in-person fitting.
- Medical advice, surgery planning, or clinical measurement.
- Guaranteeing how a specific bra style will feel on your body.
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