Japanese lingerie sizing uses a letter-number system that looks similar to European sizing but isn't. A Japanese 75B is not the same as a European 75B. If you've ordered lingerie from Japan and found it doesn't fit, the sizing system is probably why. Here's how to read it correctly.
How Japanese bra sizing works ¶
Japanese sizing uses the underbust measurement in centimetres as the band size, and a letter for cup size. So far, the same as European sizing. The difference is in how cup size is calculated. In Japanese sizing, the cup letter is determined by the difference between the bust and underbust measurements in 2.5cm increments. In European (and most UK) sizing, the increment is 2.5cm for some sizes and different for others depending on the country. A Japanese B cup corresponds to a 5cm difference; a European B cup is typically a 2.5cm difference.
A practical conversion table ¶
Japanese A = European AA. Japanese B = European A. Japanese C = European B. Japanese D = European C. Japanese E = European D. Japanese F = European DD (E in some systems). Japanese G = European E (F in some systems). For band sizes, Japanese sizing uses the actual underbust measurement, so a Japanese 65 band corresponds to a 65cm underbust, which is approximately a UK 30 band. A Japanese 70 is a UK 32, 75 is a UK 34, 80 is a UK 36.
How to measure yourself accurately ¶
Measure your underbust directly under the bust, snug but not tight, while wearing a non-padded bra or no bra. Round to the nearest 5cm for the band size. Measure your bust at the fullest point, standing straight with arms at your sides. Subtract the underbust from the bust measurement. Every 2.5cm of difference corresponds to one cup size in Japanese sizing. If the difference is 10cm, that's a Japanese D cup (European C).
What to do if you are between sizes ¶
If your measurements fall between standard sizes, the custom sizing option at checkout is the most reliable solution. It's also worth noting that cup size is not fixed across band sizes: if you go up a band size, you should go down a cup size to maintain the same cup volume (and vice versa). This is called sister sizing, and it's useful when a standard size is close but not quite right.
Sizing systems are genuinely confusing, and the differences between Japanese and European systems are specific enough that guessing usually goes wrong. Measure twice, convert carefully, and use the custom fit option if you're unsure.