J cup is a fuller size found mainly in specialty and made-to-measure ranges — worth checking a full-bust specialist rather than a general lingerie aisle.
Common J cup sizes
| Size | Sister size (band up) | Sister size (band down) |
|---|---|---|
| 30J | 32HH | 28JJ |
| 32J | 34HH | 30JJ |
| 34J | 36HH | 32JJ |
| 36J | 38HH | 34JJ |
| 38J | 40HH | 36JJ |
| 40J | 42HH | 38JJ |
Sister sizing
A 34J shares roughly the same cup volume as a 32JJ and a 36HH. Use the sister size calculator to find your full chain.
Fit tips
Shopping
Specialty brands first
Full-bust specialists are far more likely to stock this size with a properly engineered fit.
Fit check
Confirm band fit closely
At fuller cups, a slightly loose band has an outsized effect on overall support — check it carefully.
Questions
J cup FAQs
Brands and retailers that specialize in full-bust ranges are the most reliable source, since general mainstream ranges rarely stock it.
No — sizing continues beyond J in most systems, though availability narrows further as the letter goes up.
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