Most websites have size charts with measurements in inches or centimeters. Use those.

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I'm asian and I can't even wear asian clothes because my shoulders are too broad and I have actual boobs. I'm only maybe a large B. asians don't really. I mean I know people who are just completely flat. Even asian bras don't fit me. And even the armholes are cut smaller and long sleeves are shorter. It's not just the sizing that's asian, the boob cut is asian, the sleeve-holes are asian, the length is asian-proportionate. If you're an asian size like uk4-8 and you're very petite, by all means buy asian clothes, I like them sometimes. If you're a uk10-12 or larger, and you have boobs that aren't an a cup, I'd say sizing is going to be pretty difficult. If you're a US size L I'd say you're completely sized out, unless you can literally give your measurements to the seller on aliexpress and they recommend you a size XXL or XXXL or something(it exists in some kinds of more expensive asian clothing.) I'm a uk8 and I wear an asian L -XL. I think that's a U.S. size S but I'm not completely sure. I'll end off with this post which I thought was kind of rude because she basically insulted asian sizing as being doll-sized or kid-sized, when the fact is simply that most asians and most caucasians are just of different sizes and I don't think we should be insulted as being kid-sized or three feet tall, BUT it does basically demonstrate the problem of tiny arm holes and tiny lengths etc. http://suburbanturmoil.com/this-is-what-happens-when-you-order-ridiculously-cheap-clothing-from-singapore/2014/11/21/ More on reddit.com