There are
901 mi
from Lewisville, TX to Dekalb, IL
That's the driving distance. It would take 16 hours 45 mins to go from Lewisville, Texas to Dekalb, Illinois.
The flight distance (direct flight from Lewisville, TX to Dekalb, IL) is 761.40 mi.
901 mi = 1,450.34 kms