There's no international standard for clothing sizes. The system of dress sizing used in the United States of even numbers or of XS-XL is completely different from the Asian systems of sizing. If you go shopping in Tokyo or buy clothing online from an Asian source, this can lead to a huge headache or leave you stuck with a dress far too big or small. It's important to know the size conversions so you find a perfect fit.
In Japan, watch out for lettered sizes (XS-XL), as these tend to run small. If a dress made in Japan is labeled as a medium, for example, it's probably a small in the United States. Japanese manufacturers also use two separate numbered systems. The first is an arbitrary number system like our 2-4-6-8 system in the United States, and the second relies on the actual measurements of those sizes. 5-7-9-11-13-15 correspond to an American XXS-XS-S-M-L-XL, respectively. 36-38-40-42 correspond to an American XS-S-M-L, respectively.
In Korea, you'll find a simple numbered system. 44-55-66-77-88 correspond to an American XS-S-M-L-XL, respectively.
In China, watch out for two separate and more tricky systems. These two systems differ because they rely on the measurements of different parts of the clothing. An American small is 160-165 or 84-86. A medium is 165-170 or 88-90. A large is 167-172 or 92-96. Extra large is uncommon and therefore lacking in real standard measurements, but is generally 168-173 or 98-102, depending on the manufacturer.
Savannah McDermott is an instructor of English as a second language in Zafra, Spain. She has a bachelor's degree in Spanish and international studies from Indiana University. She has been writing since 2000 and has extensive experience in both academic and journalistic writing. McDermott has been published in the "Senator" and the "Indiana Daily Student," her high school and college newspapers.