The official currency of Sint Maarten (Dutch Side) is the Antillean Guilder or Florin (fls). The exchange rate is approximately 1.80 fls. for 1.00 $US.The official currency in St. Martin (French Side) is the Euro just like in France and Europe. The exchange rate is approximately 1.00 Euro to 1.50$US and changes often. The third and most popular currency on the island is the American $US Dollar. Guilders are only accepted on the Dutch side while Euros are usually only used on the French side due to the steep exchange rate. US Dollars are used absolutely everywhere but much less on the French side. It is wiser to go change your US dollars at a Currency Exchange center (There are plenty on the island) before going shopping or dining on the French side. Many French restaurants do have a special where they accept $1 for 1 Euro which is a great deal! Good luck.