How Do Japanese Sizes Convert To US Sizes?

Shopping across international size systems can be tricky because Japan and the US label and measure clothing differently. This guide explains how to convert common Japanese sizes into their closest US equivalents for clothing, pants, shoes, rings, and bras.

Key Takeaways

• Many Japanese clothing, shoe, and pant sizes are based on measurements in centimeters, such as waist size or foot length.
• US sizing usually relies on inches and general labels like Small, Medium, and Large, which can vary by brand.
• To find the most accurate sizes when doing Japanese to US size conversions, it’s best to use measurements listed on size charts.

Shopping for clothing or accessories from Japan can be confusing if you’re used to American sizing. The way measurements are labeled, calculated, and displayed often differs between the two systems. Understanding Japanese size to US sizes conversions helps both shoppers and e-commerce businesses translate those measurements so the right size is chosen the first time. 

Japanese Size to US General Size Differences

Japanese and US sizing systems often use different measurement standards and labeling formats. In many cases, Japanese measurements are based on the metric system, using centimeters to describe dimensions such as length, circumference, or height. 

The United States typically uses the imperial system, which relies on inches for the same types of measurements. Converting between the two systems usually requires a simple unit conversion, since 1 inch equals 2.54 centimeters. 

Another difference is how sizes are labeled. Japanese products and charts frequently reference the actual measurement in centimeters, while US sizing may use inches or generalized size labels. 

Japanese Clothing Sizes to US Size Conversion

Japanese and US clothing sizes follow different rules, and those rules can also vary between men’s and women’s sizing within each country.

Women’s Clothing Sizes

In Japan, women’s clothing sizes often use a numbered system such as 7, 9, 11, 13, 15, and 17. These sizes typically increase in increments of two numbers, with each step corresponding to slightly larger body measurements for bust, waist, and hips. 

In the United States, women’s clothing typically uses even-number sizes such as 2, 4, 6, or 8, along with general labels like Small, Medium, and Large. These sizes also usually increase by two as body measurements increase.

In general, US clothing sizes are about five numbers smaller than the equivalent Japanese women’s size. For example, a US size 4 typically corresponds to a Japanese size 9, while a US size 8 is often close to a Japanese size 11 or 13, depending on the brand and garment style.

Men’s Clothing Sizes

Many men’s clothing items in Japan are labeled using letter sizes like S, M, L, and LL, while more tailored garments may use measurement-based sizing. In the United States, men’s clothing often uses letter sizes such as S, M, L, and XL for casual garments, or measurements like chest, waist, collar, and inseam for more specific fits.

Men’s shirts and collars are often listed in centimeters in Japan, while US sizing for the same items is typically given in inches. A US men’s shirt collar size 14 corresponds to about a Japanese size 36, and each half-inch increase in US collar size usually equals about one centimeter in Japanese sizing.

Because of these differences, checking a clothing conversion chart can help you compare measurements such as bust, waist, hips, chest, or collar size and find the closest equivalent between the two systems.

Japanese Pants Sizes to US Size Conversion

In Japanese pants sizing, numbers like 70, 80, or 90 refer to the waist measurement in centimeters. So JP 80 simply means the pants are designed for an 80-centimeter waist. If you want to convert a Japanese pants size to a US size, you must convert centimeters to inches first, then match that number to a US size.

Here’s a simple example:

For example, a 32-inch waist converts to 80 centimeters, which is typically labeled around JP 80 on Japanese pants. This would be a size Medium in US pant sizes. 

Japanese clothing tends to be cut slightly slimmer and shorter than US versions of the same garment. So if you know you usually wear a US size Small, don’t automatically order a Japanese size Small because the item probably will not fit you correctly. 

Japanese Shoe Sizes to US Size Conversion

Japanese shoe sizes are based on foot length in centimeters. If a shoe is labeled 25 cm in Japan, it’s designed for a foot that measures about 25 centimeters from heel to toe.

The number of a US shoe size isn’t the foot length itself. Instead, the US system uses a formula based on foot length in inches and converts that measurement into a numbered scale.

Another detail that often confuses shoppers is that men’s and women’s shoe sizes are different in the US, even if their foot length is the same. In general, a US woman’s shoe size is about one to one-and-a-half sizes larger than the equivalent men’s size. 

Here’s how that might look when converting Japanese sizes:

When comparing international footwear sizes, using a shoe size conversion chart helps translate the centimeter measurement into the correct US men’s or women’s size so shoppers can choose the closest fit.

Japanese Ring Size to US Size Conversion

Japanese ring sizes and US ring sizes also use different numbering systems. Japan uses sizes 1 through 30, and each number corresponds to the inner circumference of the ring measured in millimeters.

The United States uses its own numeric scale that increases in quarter-size increments based on the ring’s inner diameter and inner circumference.

For example:

• Japanese ring size 9 → US ring size 5
• Japanese ring size 11 → US ring size 5.5-5.75
• Japanese ring size 13 → US ring size about 6–6.5, depending on the chart

Because ring sizing is based on precise measurements, most conversions rely on circumference or diameter rather than guessing based on the size label alone. 

Japanese Bra Size to US Size Conversion

Japanese and US bra sizes both use a band number and a cup letter. In Japan, band sizes are based on the underbust measurement in centimeters and increase in steps of 5 cm (65, 70, 75, 80, and so on). In the US system, band sizes are measured in inches and usually appear as 30, 32, 34, 36, and higher.

Cup Sizes

Cup sizes in both countries are calculated using the difference between the bust and underbust measurements. That number is measured in centimeters in Japan and inches in the United States.

Also, the cup letter in Japanese bra sizes typically appears before the band number, such as B70 or C75. In the US system, the band number usually comes first, such as 32B or 34C. 

When you combine the band and cup conversions, most sizes stay the same letter while the band number changes to centimeters. For example:

• US 32A → JP A70
• US 34B → JP B75
• US 36C → JP C80

These conversions match the closest equivalent measurements between the two sizing systems. 

Why Some People Size Up in Japanese Bras

Some shoppers choose to go up one cup size when buying Japanese bras. This recommendation comes from how many Japanese brands design their lingerie. Styles often include extra padding or shaping, and some cups may run slightly smaller than Western brands. Because of this, a person who normally wears 70A in Japanese sizing might find 70B more comfortable depending on the brand or style. 

Easily Convert Japanese Sizes to US Sizes With Kiwi Sizing

Understanding Japanese to US size conversions helps shoppers choose the right fit while reducing sizing confusion for online stores. Even with conversion charts, many customers still aren’t sure which size to pick. An apparel size recommender like Kiwi Sizing can display clear charts and recommend the right size directly on your product pages. 

If you want an easier way to guide customers and reduce returns, install Kiwi, the dynamic Shopify size chart app built to simplify sizing for your store.