About 30 miles by road.
DCA is Reagan International IAD is Dulles International
The nearest airports to Washington, DC are Reagan International Airport (DCA) which is right near town and Dulles Airport (IAD) which is west of town but is the major international airport for the area.
Ronald Reagan Washington National Airport (DCA) Washington Dulles International Airport (IAD) Thurgood Marshall Baltimore/Washington International Airport (BWI)
the closest airport to DC is DCA, which is in DC. another close one, which is 15-20 minutes away, is IAD.
Washington Dulles International Washington, DC Source: http://www.world-airport-codes.com
Roughly forty miles
The code is: DCA
Ronald Regan National Airport (used to be called National) is just across the Potomac from DC. It is also on the metro line so it is easy to get to. Airport code is DCA Dullas International Airport (normally called Dullas) is about 30-45 minutes from DC in northern Virginia. Airport code is IAD Baltimore Washington International Airport is north of DC towards Baltimore. It is about 45-60 minutes north of DC and you can get there off 95 North or via Amtrak or train. Airport code is BWI. Metropolitan Airport authority manages IAD and DCA
The driving distance from Ronald Reagan Washington National Airport to Washington Dulles International Airport is:30 miles / 48 km
It is DCA
While none of them are actually located inside the city, the Washington DC major airports are Ronald Reagan National Airport (DCA), Dulles International Airport (IAD) and Baltimore-Washington International Airport (BWI). Reagan is the closest to Washington, with a Metro station on-site.