Take Washington Flyer Silver Line Express Bus to Wiehle-Reston East metrorail station (silver line) Silver Line Express Bus operates every 15-20 minutes from 6am to 10:20pm for weekdays. $5 each way, cash or credit card only.
From Dulles International Airport to the Embassy: approximately $65 or above
Click the image to enlarge the Washington D.C. Metrorail Map.