J Cup Size (UK)
A UK J cup is a bust measurement 13 inches larger than the band, the thirteenth position on the UK ladder. It is not the same cup as a US J, which is the tenth position, and it is an EU M.
What is a J cup?
A J cup in UK sizing means the fullest bust measurement is 13 inches (≈ 33 cm) larger than the underbust band. In US sizing the same 13-inch difference is labelled beyond K; in EU sizing M. It is not a fixed volume: what the cup holds grows with the band it sits on.
Same letter, nine volumes. A 28J and a 44J are both “J cups”: the second holds several times the volume of the first.
Every J-cup size
The same 13-inch difference on each band. Read across for measurements, sister sizes and the EU / FR / AU labels; tap a size for its full guide.
| Size | Underbust | Bust | Sister sizes | EU · FR · AU |
|---|---|---|---|---|
| 28J | 27–28″ · 69–71 cm | 41″ · 104 cm | — · 30HH | 60M · 75M · 6J |
| 30J | 29–30″ · 74–76 cm | 43″ · 109 cm | 28JJ · 32HH | 65M · 80M · 8J |
| 32J | 31–32″ · 79–81 cm | 45″ · 114 cm | 30JJ · 34HH | 70M · 85M · 10J |
| 34J | 33–34″ · 84–86 cm | 47″ · 119 cm | 32JJ · 36HH | 75M · 90M · 12J |
| 36J | 35–36″ · 89–91 cm | 49″ · 124 cm | 34JJ · 38HH | 80M · 95M · 14J |
| 38J | 37–38″ · 94–97 cm | 51″ · 130 cm | 36JJ · 40HH | 85M · 100M · 16J |
| 40J | 39–40″ · 99–102 cm | 53″ · 135 cm | 38JJ · 42HH | 90M · 105M · 18J |
| 42J | 41–42″ · 104–107 cm | 55″ · 140 cm | 40JJ · 44HH | 95M · 110M · 20J |
| 44J | 43–44″ · 109–112 cm | 57″ · 145 cm | 42JJ · — | 100M · 115M · 22J |
The J cup, in numbers
Volume is the pairing, not the letter. At 13 inches of difference the cup is beyond the range the clinical weight studies covered, so this site does not print a weight; on a 34 band its sisters are 32JJ and 36HH.
Is a J cup big?
Thirteen inches of difference is beyond the clinical weight studies and beyond the US alphabet; it belongs to UK specialist manufacture and, past the mid-40s bands, to made-to-order. The band does almost all the work at this depth, which is why specialists draft their J bands firm.
The letter J appears in both the US and UK alphabets at different positions, so a "J cup" search returns two different sizes; this page is the UK J.
Key takeaway: “J cup” describes a 13-inch difference in UK letters. Volume depends on the band; convert by position, never by letter.
What people get wrong about J cups
Wearing a J cup on a band that rides up?
The old +4 rule inflates the band by four inches and understates the cup by two letters. If a chart gave you a J cup on a loose band, the snug-measure equivalent is two bands down and two cups up: the same volume, carried by the band.
| If a +4 chart said | Snug-measure size is likely | Same volume? |
|---|---|---|
| 32J | 28K | Yes: the band supports instead of the straps |
| 34J | 30K | Yes: the band supports instead of the straps |
| 36J | 32K | Yes: the band supports instead of the straps |
| 38J | 34K | Yes: the band supports instead of the straps |
| 40J | 36K | Yes: the band supports instead of the straps |
J cup in US, EU and other systems
4″ difference. Matches UK and EU letters.
Identical to US. Full-bust specialists (Panache, Freya, Curvy Kate) label in UK letters.
Identical to US. FR, IT, DE and JP use EU cup letters.
Convert any exact size with the size converter.
Bra styles that fit a J cup
Seamed full cups with side slings on firm, wide bands, and longlines for strapless. Nothing moulded, nothing plunge.
Frame like a 28 band, also look for narrower wires and shorter straps The same J cup is deeper and narrower here.
The widest choice of styles at this cup. Molded for a smooth line, seamed for shape and lift.
The J cup is wider and shallower; prioritise a firm, wide band and a wire that fully encloses the root. Longline and three-hook styles help.
Shape matters as much as size: see the fit guide for the five breast shapes and the constructions that suit each.
J cup: answered
How big is a UK J cup?
A UK J cup is a bust 13 inches (33 cm) larger than the band, the thirteenth UK cup letter. It is deeper than any standard US letter and equivalent to an EU M.
Is a UK J the same as a US J?
No. A US J is the tenth position (ten inches), a UK GG. A UK J is the thirteenth position (thirteen inches). Same letter, three cups apart.
What is a UK J cup in US sizes?
Beyond the standard US alphabet, which ends at K (eleven inches). Brands that cut it in US letters extend their alphabet their own way.
What are the sister sizes of a 30J?
A 28JJ and a 32HH in UK letters.
Which brands make UK J cups?
Panache (including Cleo on small bands), Sculptresse, Elomi, Curvy Kate and Fantasie on select styles; check each dossier for the bands it covers.
Opens HauteFlair’s own hub page; use your measured size there. HauteFlair is owned by the same company as Brasize.ai; that relationship never changes the sizing math, charts, or fit advice on this page. How this site makes money.
Find your exact size
A cup letter is only half the answer. Two measurements give you both halves.
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