oh my measure
by pebbly
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75K bra size

A 75K bra is cut for an underbust of 72.5–77.5 cm and a bust of 107–109 cm. Below it is the same size as every other system prints it, and the sister sizes that hold the same cup.

75K in every system

EU
75K
RU
75K
US
34K
UK
34H
FR
90K
IT
2K
JP
75K

A starred letter continues that system’s published table rather than being taken from it — European charts stop at H, British ones run further, and the same breast is published in one and extrapolated in the other.

Where each notation comes from

What each notation means — why the British band reads 34 and the Italian reads 2 — is set out system by system on the bra size page.

Sources

Nothing here is looked up in a table of equivalents: band and cup are computed once from the metric ladder, then printed in each system’s own letters (formula version 2).

  • en.wikipedia.org the underbust ladder in 5 cm steps and the AA–H cup table
  • en.wikipedia.org the British and American cup runs, the French +15 shift, the Italian numbering
  • en.wikipedia.org the "+0" and "+4" methods, sister sizes, measuring upright and leaning forward
  • ru.wikipedia.org the Russian table: the same intervals, the same letters

Checked: no date on record

Where these numbers come from

The band is the underbust rounded to the nearest five centimeters, so 72.5–77.5 cm all round to 75. The cup is how far the bust exceeds that band’s nominal value: 32–34 cm gives this letter, at two centimeters per letter starting at ten. Add them and you get a bust of 107–109 cm.

The cup is measured against the nominal 75, not against the tape. That is what every published chart does, and it is why an underbust at the bottom of this band and one at the top get the same letter despite five centimeters between them. Near a band edge, try the sister size too.

In inches, 75K is an underbust of 28.5–30.5" and a bust of 42.1–42.9". Note that the UK and US band number is not that measurement: 75 cm is 28.5–30.5", and the band is called 34H because the English notation adds four inches.

Same cup as 75K, different band

One band up is one letter down, because the cup is measured over the band — which makes 80J the same volume as 75K. In a shop the printed size that fits is routinely not the one the tape said, so these are worth trying on.

One step away

75J, 70K, 80K — a letter either side of 75K on this band, and this letter on the neighbouring bands.