There are
1,655 mi
from Gaithersburg, MD to Thornton, CO
That's the driving distance. It would take 1 day 5 hours to go from Gaithersburg, Maryland to Thornton, Colorado.
The flight distance (direct flight from Gaithersburg, MD to Thornton, CO) is 1,475.32 mi.
1,655 mi = 2,664.23 kms