Size charts for clothing can vary from country to country. With a simple formula, U.S. clothing sizes can easily be converted into Brazilian sizes. Brazil uses the European sizing method, so that simplifies things a little.
Look at the tag to make sure it's a standard U.S. size. Note whether it's a number size or small, medium, large.
For single-digit sizes, add a three in front. (A U.S. size 4 is a 34 in European and Brazilian sizes.) For double-digit sizes, replace the one with a 4. (A U.S. size 16 is a 46 in European and Brazilian sizes.)