Tourists must take cash to Iran as major credit cards, such as VISA and MasterCard, are not accepted. Tourist cards are bank-issued transaction cards in Iranian Rials, debit cards that work throughout Iran's banking network.
Iran has two exchange rates, official and street.
Iran has two exchange rates, one formally fixed by the Central Bank of Iran and another informal, open market rate that's sold to the public via currency exchange shops and traders on street corners (Street Rate).
The exchange rate varies but tourist cards are issued by banks and charge the official rate, which is the lower of the two.
Iranian Rial rate changes frequently but, on January 26, 2017, here's where it stood, per Farsinet's data:
Official => USD 32,360 =>Street => 38,490
Official => Euro 34,806 =>Street => 42,100
Official => British Pound 40,965 =>Street => 48,900
Official => Japanese Yen 285 =>Street => 345
Official => Swiss Franc 32,406=> Street => 39,000
Official => China Yuan 4,704 =>Street => 5,600
Again, Farisnet explains:
The Unofficial-Street Exchange Rate used among small businesses and private transactions was much higher than official multi-exchange-rate prior to 2002. Since going to a single exchange rate the official and "Street-rate" have come much closer. The rates listed are based on the official exchange rate posted by the Iran Central Bank. We compare the official and "Street-rates" to ensure rates listed are the most accurate indicative of the true IRR-USD exchange rate. US Dollar (USD) is the most widely used foreign currency and the new $100 bills are preferred for street transactions and get the best rate.