Bra Size Calculator Japan

Japanese bra sizing uses centimetre-based bands (65, 70, 75…) with its own cup letter progression. This free Japan bra size calculator estimates your Japanese bra size from two simple tape measurements, in inches or centimetres, in under a minute.

Here is how it works. Enter your underbust — measured snugly right under your bust — and your bust — measured around the fullest part. The calculator sets your band from the underbust and your cup from the difference between the two. Use Simple mode for the quick estimate, or Advanced mode for a refined result from six measurements.

Your result is an estimate and a starting point, never a guarantee of fit. Brands cut differently, so always check the brand’s own size chart when you can.

Enter Your Measurements

Not sure how to measure? See how to measure your bra size.

How to Measure for a JP Bra Size

  1. Measure your underbust. Wrap a soft tape snugly around your ribcage, directly under your bust, keeping it level all the way around.
  2. Measure your bust. Wrap the tape around the fullest part of your bust, level and firm but not tight.
  3. Enter both numbers above in inches or centimeters and press Calculate.

For the full walkthrough, see how to measure your bra size.

Japan Bra Size Chart

Common JP sizes by band and cup. Scroll sideways on small screens.

BandABCDEFG
6565A65B65C65D65E65F65G
7070A70B70C70D70E70F70G
7575A75B75C75D75E75F75G
8080A80B80C80D80E80F80G
8585A85B85C85D85E85F85G
9090A90B90C90D90E90F90G
9595A95B95C95D95E95F95G

Commonly stocked Japanese sizes. Japanese brands tend to run smaller in the cup than Western brands — when between sizes, consider sizing up one cup.

How JP Bra Sizing Works

Band sizes

Japanese bands are your underbust in centimetres, rounded to the nearest 5: 65, 70, 75, 80 and so on. A 30-inch underbust (about 76 cm) gives a 75 band; a 34-inch underbust (about 86 cm) gives an 85.

Cup sizes

Japanese cup letters run A, B, C, D, E, F, G, H, I, J, K, one step per inch of difference between bust and band, counted from A. Because counting starts at A (with no AA), the same difference can read one letter higher than in US sizing.

A worked example

For example, a 30-inch underbust (about 76 cm) and a 33-inch bust give an estimated 75D in Japanese sizing.

JP Size Conversions

Closest standard equivalents at the same body size:

US sizeUK sizeJP size
30C30C75D
32C32C80E
34C34C85E
36D36D90F

Each row shows the sizes this calculator gives for the same measurements in each system — the closest standard equivalents. Japanese cups can run small versus Western brands, so treat conversions as a starting point.

JP Sister Sizes

Go down a band and up a cup, or up a band and down a cup, to keep a similar cup volume. For example, a 75D wearer might also try its one-band-up and one-band-down neighbours. Use our sister size calculator or read the sister sizes guide.

Common Measuring Mistakes

  • A tape that is not level. Check in a mirror that the tape runs horizontally front and back.
  • Measuring over a padded bra. Padding inflates the bust reading and the cup result.
  • Guessing instead of measuring. Bodies change; a fresh two-minute measurement beats years of habit.
  • Ignoring brand differences. The calculator gives a starting size — the brand’s own chart has the final word.

Frequently Asked Questions

How do Japanese band sizes work?

Japanese bands are your underbust in centimetres, rounded to the nearest 5: 65, 70, 75, 80 and so on. A 30-inch underbust (about 76 cm) is a 75 band; 34 inches (about 86 cm) is an 85 band.

Do Japanese cups run small?

Many shoppers find Japanese cups run slightly small compared with US/UK brands. If you are between sizes, sizing up one cup is a common approach — and always check the brand’s own chart.

What is the difference between JP and EU sizing?

Both number bands the same way (underbust in centimetres, rounded to the nearest 5). The cup ranges differ: JP runs to K while EU stops at H, so very full cups can read one letter higher in JP — for example, the same fuller measurements give 95I in JP and 95H in EU here.

Can I use inch measurements?

Yes — select Inches and the calculator converts to centimetres internally before applying the Japanese band rule.

Where can I buy Japanese sizes outside Japan?

Specialty online retailers and Japanese department-store web shops ship internationally. Knowing your JP size plus one cup up gives you options when stock is limited.

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