There are
2,800 mi
from Gaithersburg, MD to San Bruno, CA
That's the driving distance. It would take 2 days 1 hour to go from Gaithersburg, Maryland to San Bruno, California.
The flight distance (direct flight from Gaithersburg, MD to San Bruno, CA) is 2,425.12 mi.
2,800 mi = 4,506.54 kms