How the conversion works
Starting from a US/UK band and cup, each region applies its own known relationship: EU and France convert the band to centimetres, Australia and Canada mirror the UK and US directly, and Japan recalculates using its own centimetre-based cup formula rather than a straight translation.
Japan: recalculated from cm-based cup steps, not a direct cup-letter swap
Because Japan's formula genuinely differs rather than just relabeling the same gap, treat that row as a close approximation rather than an exact one-to-one match.
Questions
Conversion FAQs
UK and US cup letters match up to a D cup, then diverge — the conversion tool accounts for this automatically above a D.
It's a close standard approximation based on published band conversions; individual brands sometimes round slightly differently.
Japan's JIS system uses a different underlying formula rather than a direct translation of the inch-based scale, so the conversion is a close estimate rather than an exact rule.
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