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How Japan Sizing Actually Works
A Japanese band size is close to your actual underbust in centimeters rounded to the nearest 5, with cup letters generally matching the EU-style scale.
This makes Japanese sizing numerically the most different from US/UK sizing of any system on this page. Always run the conversion rather than guessing.
Convert Your Size
Use the calculator above to see your size across all 7 systems this site supports, Japan included. If you already know your size in another system, enter it into the Global Bra Size Converter instead of doing the math by hand.
Getting an Accurate Starting Point
No conversion is more accurate than the measurement it’s based onHow to Measure covers the exact technique this calculator assumes, and the Sister Size Calculator is worth trying if your first result doesn’t feel quite right.
A Worked Example for Japan
Say your underbust measures 36 inches and your bust measures 40 inches. A US 36D.
Converted to Japan’s system, that becomes roughly 90cm D using the formula above. Run your own numbers through the calculator on this page rather than eyeballing the conversion. Small rounding differences near a size boundary can shift the result by a full cup letter.
Shopping Locally vs. Importing in Japan
Japanese department stores are known for detailed, unhurried fitting appointments, and staff will typically re-measure you on the spot rather than relying on a self-reported size.
Common Sizing Mistakes Shoppers Make in Japan
A frequent mistake among shoppers converting into Japan’s system is applying the EU +16cm padding formula instead of Japan’s raw-underbust approach, which overstates the band by a meaningful margin.
Shoppers also sometimes apply Japan’s raw-cm band formula to Korean sizing, when the two are close but not always identically rounded.
A Note on Retail Fitting in Japan
Japanese department store fittings are famously thorough and unhurried, with staff typically re-measuring rather than trusting a self-reported size.
Why Japan’s System Looks Different at First Glance
Japan’s centimeter-based band measurement without the extra padding used in the EU formula can make a Japanese size look smaller on paper than the equivalent Western size. It’s a different reference point, not a smaller actual fit.
A Sizing System Built Around Precision Measurement
Japanese retail culture places a strong emphasis on precise, professionally-guided measurement, and department store fitting services remain a common and trusted resource for finding an accurate size rather than relying solely on self-measurement.
Limited Overlap With Western Extended Sizing
Historically, Japanese mainstream retail has offered a narrower cup-letter range than some Western markets, meaning shoppers at either end of the size spectrum sometimes need to look at import options or specialty retailers for full coverage.
Seasonal Product Cycles Are Common
Japanese retailers often rotate seasonal collections more frequently than some Western markets, which can mean a specific size or style available one season may not be restocked identically the next. Worth buying when you find the right fit.
