The calculated distance (air line) between Dehiwala-Mount Lavinia and Dambulla is approximately 88 miles respectively 142 kilometers.
By car or train, the actual journey to Dambulla is certainly longer, as only the direct route (as the crow flies) between Dehiwala-Mount Lavinia and Dambulla has been calculated here.
Air line (approximately)
142 kilometers
77 nautical miles