There are
475 mi
from Clarksville, TN to Dekalb, IL
That's the driving distance. It would take 9 hours 9 mins to go from Clarksville, Tennessee to Dekalb, Illinois.
The flight distance (direct flight from Clarksville, TN to Dekalb, IL) is 380.42 mi.
475 mi = 764.11 kms