Calculating American duties on imported goods is a very difficult task. We have a more general discussion of what is involved on our page titled “What will it cost?”
Experts spend years learning how to properly classify an item in order to determine its correct duty rate. The U.S. Customs and Border Patrol provides the following example on what you need to consider when importing a wool suit. To get to the duty rate you will need to know things like: does it have darts? Did the wool come from Israel or another country that qualifies for duty-free treatment for certain of its products? Where was the suit assembled, does it have any synthetic fibers in the lining?