Standardize Asian Clothe Sizes?

Hi all
Has anyone attempted to standardize Asian clothes sizes and convert them into American?
I have a tshirt store and get constant questions about size in regular American.
Anyone has any experience converting the variations to US size and how did that all work with order fill-outs and such?
Also any size chart you're using that is not all over the place like every ali store has different ones, some are not even readable.

Thank you!