30J Bra Size, In Full
A 30J is a 30-inch band carrying a J cup: a 10-inch difference between bust and underbust. Here are its measurements, its labels in every system, its sister sizes, and where it actually exists on shelves.
30J in UK, EU, FR, AU & IT sizing
Cup alphabets diverge above D: the UK letter here is not a typo. The converter handles every system.
What works at this size
This is engineered-garment territory, and it is well served: full-bust specialists build these cups with four-part seaming, side-support slings, reinforced wire channels and four-hook bands as standard. The construction is genuinely better than mainstream sizes receive: the trade is a narrower style range.
Where to find it
US I–K cups live mainly under their UK names (GG in the UK alphabet) at the full-bust specialists: Panache, Elomi, Fantasie and Freya carry them as core sizes. When shopping UK sites, convert the letter first (the converter does it instantly); the band number stays the same.
Is 30J actually your size?
Five checks decide: band level and snug on the loosest hook; cups smooth with no gap or spill; gore flat on the sternum; wires on ribcage, not tissue; straps resting. Anything failing has a page: the fix guides decode every symptom, and the calculator re-answers the size question from two measurements.
30J: answered
What are the measurements for a 30J bra size?
A snug underbust of about 29–31 inches (74–79 cm) and a full bust around 40 inches (99–104 cm): a difference of roughly 10 inches, which is the J cup on this band. Measured snug, with no +4 added.
What is 30J in UK and European sizing?
30GG in the UK and 65J in EU/German sizing (FR/ES 80J). The band converts by table; the cup letter changes alphabet above D, which is why checking both parts matters.
Is 30J a common size?
Under its US letter, rarely stocked, but under its UK name (30GG) it is a standard size at full-bust specialists like Panache, Elomi, Fantasie and Freya.
HauteFlair labels cups in UK letters, so these links already convert your size by position (a US DDD lands on a UK E, a US G on a UK F). 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.
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Two measurements, no inches added, sister sizes attached.
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