When shopping overseas, a merchant may ask you if you would like to convert your credit card transaction from the local currency into U.S. dollars. This is called Dynamic Currency Conversion (DCC), and while it may sound like an enticing offer, this conversion is very expensive for the cardholder and should be avoided.
Generally, when an overseas merchant makes this offer, they will use a conversion rate that is far higher than the actual going rate, as high as 7 percent, and pocket the difference as a fee. They get away with it because many customers are not checking the math at point of sale to make sure the conversion was accurate.