There are
2,640 mi
from Rockville, MD to Simi Valley, CA
That's the driving distance. It would take 1 day 23 hours to go from Rockville, Maryland to Simi Valley, California.
The flight distance (direct flight from Rockville, MD to Simi Valley, CA) is 2,310.35 mi.
2,640 mi = 4,248.58 kms