These rates are based on live interbank foreign exchange rates and no more that 12 minutes behind the most recent trade. Typically you can expect to achieve a buying or selling rate no more than a couple of % points different from these rates at the time of your trade. Rates are however subject to both small and large fluctuations based on market forces, That is why you will always be provided with a confirmation of the trading rate by a dealer or broker prior to signing in agreement to buy of sell the currency.