Lost in Sizing Translation

European imports like Moschino, Zara, Mango and H&M are wildly popular. I know. I buy those brands quite often.

But try translating the sizes to American. For example, when I try on an H&M jacket (as shown) in my regular size, it feels two sizes too small.

What's a person to do when they shop online?

Read: Shopping Locally, But Sizing Globally