Here is an article from bankrate.com on the subject.
This was taken from
http://www.bankrate.com/brm/news/cc/20050624b1.asp
"Most credit card issuers charge currency conversion fees for foreign purchases made with their credit cards, debit and check cards, and ATM cash withdrawals. Over the course of your travels, that can add up to a significant increase in the cost of your vacation -- money you could save by picking the right credit card.
The fees are twofold: Visa and MasterCard have a standard 1 percent charge on foreign purchases and the issuing bank adds another fee.
In the chart below, the percentage shown below each credit card issuer is the total of the fees: the amount charged by the issuer, plus the charge by Visa or MasterCard for a foreign purchase. For that 1 percent fee, Visa or MasterCard converts your foreign-currency purchase to U.S. dollars. All Visa or MasterCard cards carry that 1 percent charge.
The credit card issuer or bank often charges an additional fee, usually 2 percent, which adds up to a 3 percent total charge on foreign purchases. Bankrate contacted several credit card issuers and all refused to explain the reason for the charge.
The percentage posted under debit- and checking-card purchases is the charge assessed by both Visa or MasterCard and the credit card issuer or bank. A fee is also assessed by each card issuer and bank for ATM cash withdrawals. ATM charges vary for each card.
The table of major credit card companies and their currency-conversion-fee policies was correct as of December 2007. The data were originally collected by Bankrate researchers in October 2005.
Write to
editors@bankrate.com if you are aware of an update not shown here.
Please note that the percentage shown includes the 1-percent charge Visa and MasterCard charge for foreign-currency conversion."