The calculated distance (air line) between Dehiwala-Mount Lavinia and Welisara is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to Welisara is certainly longer, as only the direct route (as the crow flies) between Dehiwala-Mount Lavinia and Welisara has been calculated here.
Air line (approximately)
21 kilometers
11 nautical miles